Real-rooted atlas

A143494: Triangle read by rows: 2-Stirling numbers of the second kind.

A143494 nonnegative coefficients

Proved for all n: all roots real, in (−∞, 0) · coefficients of one sign · interlacing (weak) · Hadamard kernel basis map preserves real roots what this means

Recurrence from OEIS A143494
\(P_{n}(x) = \left(2 + x\right)\,P_{n-1}(x) + \left(x\right)\,P_{n-1}'(x)\)
\(P_{1}(x) = 1\)

Rows ?

nx0x1x2x3x4x5x6x7x8x9x10x11x12x13x14Pn(1)
111
2213
345110
48199137
5166555141151
632211285125201674
76466513519102452713263
8128205960695901238043435117007
92566305263353557420181541871444194828
105121917111164520420515666058107111301110541562595
11102458025465751113267011441655634091471472112016506513535027
1220481750991921029612910179976605088028174058533722737620236577123430840
1340965273457859215325665345411506143613856190127084775628713427636353289901163254885
14819215861313196420517069188535725690035941205319571552061993360119098981413412103103445910411192059223
15163844766585129442951885423630231423328528731412711925136213753655760181092340274574302650648161070591511919097183602

Generated b-files: A005493 (row sums), A126351 (reversed triangle), A138378 (row sums), A143494 ?

Computed in your browser ?

Technical details
Node id
n-6aaec68d653cbdb0 · revision 2 · JSON
Definition source
oeis_catalog:A143494
Fingerprint
f6-b5f1389370a379f1

Observed on the stored rows ?

  • Degrees: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 (affine: slope 1, intercept -1)
  • Palindromic rows: no
  • γ-positive (gamma_positive): no
  • Nonnegative coefficients (nonn): yes
  • Only rational roots (rr_by_factors: every nonzero row is a product of linear factors over ℚ): no

OEIS matches ?

A generated b-file is computed from the node's definition along the row alignment of its OEIS link and starts at the entry's offset. It is an identification on a finite prefix, not a proof that the node and the OEIS entry agree for every n.

OEIS submission text ?

Fields to paste into an OEIS submission: the example %e, the formula %F and programs %t (Mathematica) and %o (PARI/GP) that list the same rows. For an OEIS link the row numbers, the offset and the orientation are those of the entry, as matched; the matched terms were compared with the published ones, which identifies the node with the entry on a finite prefix, not for every n. The PARI/GP program is not machine-checked here.

The atlas's own rows: n = 1, …, ascending powers of x
%e Example
Triangle begins:
   1:   1;
   2:   2,     1;
   3:   4,     5,      1;
   4:   8,    19,      9,      1;
   5:  16,    65,     55,     14,      1;
   6:  32,   211,    285,    125,     20,     1;
   7:  64,   665,   1351,    910,    245,    27,     1;
   8: 128,  2059,   6069,   5901,   2380,   434,    35,    1;
   9: 256,  6305,  26335,  35574,  20181,  5418,   714,   44,  1;
  10: 512, 19171, 111645, 204205, 156660, 58107, 11130, 1110, 54, 1;
%F Formula
The row polynomials satisfy P(n,x) = (2+x)*P(n-1,x) + x*d/dx P(n-1,x) for n >= 2, with P(1,x) = 1.
%t Mathematica
P[1, x_] := 1;
P[n_, x_] := P[n, x] = Expand[(2 + x)*P[n - 1, x] + x*D[P[n - 1, x], x]];
Table[CoefficientList[P[n, x], x], {n, 1, 10}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N)); v[1] = 1; for(n = 2, N, my(i = n); v[i] = (2 + x)*v[i - 1] + x*deriv(v[i - 1], x)); v};
row(n, p) = {my(c = Vecrev(p)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i, v[i])))};
T(10)

Generated with polytool c48629374597.

A126351: reversed triangle, offset 1, from the row P1
%e Example
Triangle begins:
   1: 1;
   2: 1,  2;
   3: 1,  5,    4;
   4: 1,  9,   19,     8;
   5: 1, 14,   55,    65,    16;
   6: 1, 20,  125,   285,   211,     32;
   7: 1, 27,  245,   910,  1351,    665,     64;
   8: 1, 35,  434,  2380,  5901,   6069,   2059,    128;
   9: 1, 44,  714,  5418, 20181,  35574,  26335,   6305,   256;
  10: 1, 54, 1110, 11130, 58107, 156660, 204205, 111645, 19171, 512;
%F Formula
Row n lists the coefficients of P(n,x) in descending powers of x, where P(n,x) = (2+x)*P(n-1,x) + x*d/dx P(n-1,x) for n >= 2, with P(1,x) = 1.
%t Mathematica
P[1, x_] := 1;
P[n_, x_] := P[n, x] = Expand[(2 + x)*P[n - 1, x] + x*D[P[n - 1, x], x]];
Table[Reverse[PadRight[CoefficientList[P[n, x], x], n]], {n, 1, 10}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N)); v[1] = 1; for(n = 2, N, my(i = n); v[i] = (2 + x)*v[i - 1] + x*deriv(v[i - 1], x)); v};
row(n, p) = {my(c = Vecrev(p)); c = concat(c, vector(n - #c)); c = Vecrev(c); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i, v[i])))};
T(10)

Generated with polytool c48629374597.

A143494: triangle, offset 2, from the row P1
%e Example
Triangle begins:
   2:   1;
   3:   2,     1;
   4:   4,     5,      1;
   5:   8,    19,      9,      1;
   6:  16,    65,     55,     14,      1;
   7:  32,   211,    285,    125,     20,     1;
   8:  64,   665,   1351,    910,    245,    27,     1;
   9: 128,  2059,   6069,   5901,   2380,   434,    35,    1;
  10: 256,  6305,  26335,  35574,  20181,  5418,   714,   44,  1;
  11: 512, 19171, 111645, 204205, 156660, 58107, 11130, 1110, 54, 1;
%F Formula
The row polynomials satisfy P(n,x) = (2+x)*P(n-1,x) + x*d/dx P(n-1,x) for n >= 3, with P(2,x) = 1.
%t Mathematica
P[2, x_] := 1;
P[n_, x_] := P[n, x] = Expand[(2 + x)*P[n - 1, x] + x*D[P[n - 1, x], x]];
Table[PadRight[CoefficientList[P[n, x], x], n - 1], {n, 2, 11}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N - 1)); v[1] = 1; for(n = 3, N, my(i = n - 1); v[i] = (2 + x)*v[i - 1] + x*deriv(v[i - 1], x)); v};
row(n, p) = {my(c = Vecrev(p)); c = concat(c, vector(n - 1 - #c)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i + 1, v[i])))};
T(11)

Generated with polytool c48629374597.

Proved properties

  • Real-rooted. Every row P_n, n >= 1, is zero or real-rooted with all roots in (-inf, 0)
    Every polynomial of the sequence has only real roots, inside the stated interval.
    by the cited steps: e-d198e25506383784
  • Coefficients of one sign. Every nonzero row, n >= 1: the coefficients of P_n have one sign
    All coefficients of each polynomial have the same sign (after x -> -x when alternating).
    derived from the cited steps by a stated theorem: e-34c9c7195bdd20aa, e-d198e25506383784
  • Hadamard kernel (Malo). Rows P_n, n >= 1, are Hadamard kernels (preserve real-rootedness)
    Multiplying the coefficients of any real-rooted polynomial termwise by those of a row (Hadamard product) gives a real-rooted polynomial again.
    derived from the cited steps by a stated theorem: e-34c9c7195bdd20aa, e-d198e25506383784
  • Interlacing of consecutive rows. Rows P_(m-1), P_m interlace (weak, previous interlaces next) for every m >= 2
    The roots of consecutive polynomials alternate on the real line.
    by the cited steps: e-d198e25506383784
  • Basis map preserves real-rootedness. Basis map u^k -> P_k sends roots in (-inf, 2] to roots in (-inf, 0]: source (-inf, a + b h + kappa m] = (-inf, 2] with m = 0, target (-inf, 0]
    The linear map sending x^k to the k-th polynomial of the sequence turns polynomials with roots in one interval into real-rooted ones.
    by the cited steps: e-01c9da0321cbaf51
  • Real-rooted. Every row P_n, n >= 1, is zero or real-rooted with all roots in (-inf, 0]
    Every polynomial of the sequence has only real roots, inside the stated interval.
    by the cited steps: e-34c9c7195bdd20aa
  • Interlacing of consecutive rows. Rows P_(m-1), P_m interlace (weak, unordered) for every m >= 2
    The roots of consecutive polynomials alternate on the real line.
    by the cited steps: e-34c9c7195bdd20aa

Proof chains

3 incoming proof steps. Each step is expanded back to the roots of the proof DAG, the theorem checks of a node's own rule. JSON

Used in 9 proof steps

Same fingerprint (19)

Equal up to content, sign, reversal and a small index shift.

References

  1. [LW07] Lily L. Liu and Yi Wang. A unified approach to polynomial sequences with only real zeros. Advances in Applied Mathematics, 38(4):542–560, May 2007. doi:10.1016/j.aam.2006.02.003
  2. [MW08] Shi-Mei Ma and Yi Wang. q-Eulerian polynomials and polynomials with only real zeros. The Electronic Journal of Combinatorics, 15(1):Research Paper 17, January 2008. doi:10.37236/741
  3. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.