Real-rooted atlas

A106246: Number triangle T(n,k)=C(n,k)C(2,n-k).

A023531 → (1/2)D²+2D+1

A106246 nonnegative coefficients

Proved for all n: all roots real, in (−∞, 0] · coefficients of one sign · Hadamard kernel what this means

Recurrence from OEIS A106246
\(P_{n}(x) = \left(3\,x\right)\,P_{n-1}(x) + \left(-3\,x^{2}\right)\,P_{n-2}(x) + \left(x^{3}\right)\,P_{n-3}(x)\)
\(P_{0}(x) = 1\)
\(P_{1}(x) = 2 + x\)
\(P_{2}(x) = 1 + 4\,x + x^{2}\)

Rows ?

nx0x1x2x3x4x5x6x7x8x9x10x11x12x13x14Pn(1)
011
1213
21416
3036110
40068115
50001010121
600001512128
7000002114136
80000002816145
900000003618155
10000000004520166
110000000005522178
1200000000006624191
130000000000078261105
1400000000000091281120

Generated b-files: A106246 ?

Computed in your browser ?

Technical details
Node id
n-1815d3e1c9c57d5b · revision 1 · JSON
Definition source
oeis_catalog:A106246
Fingerprint
f6-d5b12dcc66b60731

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 0)
  • 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 = 0, …, ascending powers of x
%e Example
Triangle begins:
  0: 1;
  1: 2, 1;
  2: 1, 4, 1;
  3: 0, 3, 6,  1;
  4: 0, 0, 6,  8,  1;
  5: 0, 0, 0, 10, 10,  1;
  6: 0, 0, 0,  0, 15, 12,  1;
  7: 0, 0, 0,  0,  0, 21, 14,  1;
  8: 0, 0, 0,  0,  0,  0, 28, 16,  1;
  9: 0, 0, 0,  0,  0,  0,  0, 36, 18, 1;
%F Formula
The row polynomials satisfy P(n,x) = 3*x*P(n-1,x) - 3*x^2*P(n-2,x) + x^3*P(n-3,x) for n >= 3, with P(0,x) = 1, P(1,x) = 2 + x, P(2,x) = 1 + 4*x + x^2.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 2 + x;
P[2, x_] := 1 + 4*x + x^2;
P[n_, x_] := P[n, x] = Expand[3*x*P[n - 1, x] - 3*x^2*P[n - 2, x] + x^3*P[n - 3, x]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 2 + x; v[3] = 1 + 4*x + x^2; for(n = 3, N, my(i = n + 1); v[i] = 3*x*v[i - 1] - 3*x^2*v[i - 2] + x^3*v[i - 3]); v};
row(n, p) = {my(c = Vecrev(p)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i - 1, v[i])))};
T(9)

Generated with polytool c48629374597.

A106246: triangle, offset 0, from the row P0
%e Example
Triangle begins:
  0: 1;
  1: 2, 1;
  2: 1, 4, 1;
  3: 0, 3, 6,  1;
  4: 0, 0, 6,  8,  1;
  5: 0, 0, 0, 10, 10,  1;
  6: 0, 0, 0,  0, 15, 12,  1;
  7: 0, 0, 0,  0,  0, 21, 14,  1;
  8: 0, 0, 0,  0,  0,  0, 28, 16,  1;
  9: 0, 0, 0,  0,  0,  0,  0, 36, 18, 1;
%F Formula
The row polynomials satisfy P(n,x) = 3*x*P(n-1,x) - 3*x^2*P(n-2,x) + x^3*P(n-3,x) for n >= 3, with P(0,x) = 1, P(1,x) = 2 + x, P(2,x) = 1 + 4*x + x^2.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 2 + x;
P[2, x_] := 1 + 4*x + x^2;
P[n_, x_] := P[n, x] = Expand[3*x*P[n - 1, x] - 3*x^2*P[n - 2, x] + x^3*P[n - 3, x]];
Table[PadRight[CoefficientList[P[n, x], x], n + 1], {n, 0, 9}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 2 + x; v[3] = 1 + 4*x + x^2; for(n = 3, N, my(i = n + 1); v[i] = 3*x*v[i - 1] - 3*x^2*v[i - 2] + x^3*v[i - 3]); 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(9)

Generated with polytool c48629374597.

Proved properties

  • Real-rooted. Every row P_n, n >= 0, 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-0c9044372fd705ed
  • Coefficients of one sign. Every nonzero row, n >= 0: 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-0c9044372fd705ed
  • Hadamard kernel (Malo). Rows P_n, n >= 0, 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-0c9044372fd705ed

Proof chains

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

Used in 7 proof steps

Same fingerprint (2)

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

References

  1. [ASW52] Michael Aissen, I. J. Schoenberg and A. M. Whitney. On the generating functions of totally positive sequences I. Journal d’Analyse Mathématique, 2(1):93–103, 1952. doi:10.1007/BF02786970
  2. [AW24] Christos A. Athanasiadis and David G. Wagner. Veronese sections and interlacing matrices of polynomials and formal power series. arXiv:2404.12989. arXiv
  3. [Edr53] Albert Edrei. Proof of a Conjecture of Schoenberg on the Generating Function of a Totally Positive Sequence. Canadian Journal of Mathematics, 5:86–94, 1953. doi:10.4153/CJM-1953-010-3
  4. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.