Real-rooted atlas

A257617: Triangle read by rows: T(n,k) = t(n-k, k); t(n,m) = f(m)*t(n-1,m) + f(n)*t(n,m-1), where f(x) = 7*x + 2.

A257617 palindromic γ-positive nonnegative coefficients

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

Recurrence from OEIS A257617
\(P_{n}(x) = \left(2 - 5\,x + 7\,n x\right)\,P_{n-1}(x) + \left(7\,x - 7\,x^{2}\right)\,P_{n-1}'(x)\)
\(P_{0}(x) = 1\)

Rows ?

nx0x1x2x3x4x5x6x7Pn(1)
011
1224
2436444
383883888792
41636761241636761619800
532335642832042832043356432633600
66430326055381841302738455381843032606424710400
71282732156998315644657753524657753529983156427321561281136678400

Show all 15 stored rows

Generated b-files: A144827 (row sums), A257617, A257617 (reversed triangle) ?

Computed in your browser ?

Technical details
Node id
n-5b7da9f56b3380cb · revision 1 · JSON
Definition source
oeis_catalog:A257617
Fingerprint
f6-1edf773d06ca8d1b

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: yes
  • γ-positive (gamma_positive): yes
  • 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,         2;
  2:   4,        36,           4;
  3:   8,       388,         388,            8;
  4:  16,      3676,       12416,         3676,            16;
  5:  32,     33564,      283204,       283204,         33564,            32;
  6:  64,    303260,     5538184,     13027384,       5538184,        303260,           64;
  7: 128,   2732156,    99831564,    465775352,     465775352,      99831564,      2732156,         128;
  8: 256,  24595932,  1717519888,  14406600964,   27946521120,   14406600964,   1717519888,    24595932,       256;
  9: 512, 221378236, 28734710740, 406922697244, 1371439869268, 1371439869268, 406922697244, 28734710740, 221378236, 512;
%F Formula
The row polynomials satisfy P(n,x) = (2+(7*n-5)*x)*P(n-1,x) + (7*x-7*x^2)*d/dx P(n-1,x) for n >= 1, with P(0,x) = 1.
%t Mathematica
P[0, x_] := 1;
P[n_, x_] := P[n, x] = Expand[(2 + (7*n - 5)*x)*P[n - 1, x] + (7*x - 7*x^2)*D[P[n - 1, x], x]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N + 1)); v[1] = 1; for(n = 1, N, my(i = n + 1); v[i] = (2 + (7*n - 5)*x)*v[i - 1] + (7*x - 7*x^2)*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 - 1, v[i])))};
T(9)

Generated with polytool c48629374597.

A257617: triangle, offset 0, from the row P0
%e Example
Triangle begins:
  0:   1;
  1:   2,         2;
  2:   4,        36,           4;
  3:   8,       388,         388,            8;
  4:  16,      3676,       12416,         3676,            16;
  5:  32,     33564,      283204,       283204,         33564,            32;
  6:  64,    303260,     5538184,     13027384,       5538184,        303260,           64;
  7: 128,   2732156,    99831564,    465775352,     465775352,      99831564,      2732156,         128;
  8: 256,  24595932,  1717519888,  14406600964,   27946521120,   14406600964,   1717519888,    24595932,       256;
  9: 512, 221378236, 28734710740, 406922697244, 1371439869268, 1371439869268, 406922697244, 28734710740, 221378236, 512;
%F Formula
The row polynomials satisfy P(n,x) = (2+(7*n-5)*x)*P(n-1,x) + (7*x-7*x^2)*d/dx P(n-1,x) for n >= 1, with P(0,x) = 1.
%t Mathematica
P[0, x_] := 1;
P[n_, x_] := P[n, x] = Expand[(2 + (7*n - 5)*x)*P[n - 1, x] + (7*x - 7*x^2)*D[P[n - 1, x], 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; for(n = 1, N, my(i = n + 1); v[i] = (2 + (7*n - 5)*x)*v[i - 1] + (7*x - 7*x^2)*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(9)

Generated with polytool c48629374597.

A257617: reversed triangle, offset 0, from the row P0
%e Example
Triangle begins:
  0:   1;
  1:   2,         2;
  2:   4,        36,           4;
  3:   8,       388,         388,            8;
  4:  16,      3676,       12416,         3676,            16;
  5:  32,     33564,      283204,       283204,         33564,            32;
  6:  64,    303260,     5538184,     13027384,       5538184,        303260,           64;
  7: 128,   2732156,    99831564,    465775352,     465775352,      99831564,      2732156,         128;
  8: 256,  24595932,  1717519888,  14406600964,   27946521120,   14406600964,   1717519888,    24595932,       256;
  9: 512, 221378236, 28734710740, 406922697244, 1371439869268, 1371439869268, 406922697244, 28734710740, 221378236, 512;
%F Formula
Row n lists the coefficients of P(n,x) in descending powers of x, where P(n,x) = (2+(7*n-5)*x)*P(n-1,x) + (7*x-7*x^2)*d/dx P(n-1,x) for n >= 1, with P(0,x) = 1.
%t Mathematica
P[0, x_] := 1;
P[n_, x_] := P[n, x] = Expand[(2 + (7*n - 5)*x)*P[n - 1, x] + (7*x - 7*x^2)*D[P[n - 1, x], x]];
Table[Reverse[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; for(n = 1, N, my(i = n + 1); v[i] = (2 + (7*n - 5)*x)*v[i - 1] + (7*x - 7*x^2)*deriv(v[i - 1], x)); v};
row(n, p) = {my(c = Vecrev(p)); c = concat(c, vector(n + 1 - #c)); c = Vecrev(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-f4ea85fa593cfea8
  • 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-f4ea85fa593cfea8
  • 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-f4ea85fa593cfea8
  • Interlacing of consecutive rows. Rows P_(m-1), P_m interlace (weak, previous interlaces next) for every m >= 1
    The roots of consecutive polynomials alternate on the real line.
    by the cited steps: e-f4ea85fa593cfea8

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 3 proof steps

No candidate equalities or related sequences.

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