Real-rooted atlas

A257615: 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) = 2*x + 5.

A257615 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 A257615
\(P_{n}(x) = \left(5 + 3\,x + 2\,n x\right)\,P_{n-1}(x) + \left(2\,x - 2\,x^{2}\right)\,P_{n-1}'(x)\)
\(P_{0}(x) = 1\)

Rows ?

nx0x1x2x3x4x5x6x7Pn(1)
011
15510
2257025120
31257157151251680
4625638012870638062526880
5312552785186010186010527853125483840
615625416370236029540922202360295416370156259676800
778125318021527488205756982557569825527488205318021578125212889600

Show all 15 stored rows

Generated b-files: A051582 (row sums), A257615, A257615 (reversed triangle) ?

Computed in your browser ?

Technical details
Node id
n-3f0a1785078e99be · revision 1 · JSON
Definition source
oeis_catalog:A257615
Fingerprint
f6-228747572dae81fc

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:       5,         5;
  2:      25,        70,         25;
  3:     125,       715,        715,         125;
  4:     625,      6380,      12870,        6380,         625;
  5:    3125,     52785,     186010,      186010,       52785,        3125;
  6:   15625,    416370,    2360295,     4092220,     2360295,      416370,       15625;
  7:   78125,   3180215,   27488205,    75698255,    75698255,    27488205,     3180215,      78125;
  8:  390625,  23745880,  301457500,  1245003880,  1968154630,  1245003880,   301457500,   23745880,    390625;
  9: 1953125, 174424285, 3164289220, 18819820180, 44261068390, 44261068390, 18819820180, 3164289220, 174424285, 1953125;
%F Formula
The row polynomials satisfy P(n,x) = (5+(2*n+3)*x)*P(n-1,x) + (2*x-2*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[(5 + (2*n + 3)*x)*P[n - 1, x] + (2*x - 2*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] = (5 + (2*n + 3)*x)*v[i - 1] + (2*x - 2*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.

A257615: triangle, offset 0, from the row P0
%e Example
Triangle begins:
  0:       1;
  1:       5,         5;
  2:      25,        70,         25;
  3:     125,       715,        715,         125;
  4:     625,      6380,      12870,        6380,         625;
  5:    3125,     52785,     186010,      186010,       52785,        3125;
  6:   15625,    416370,    2360295,     4092220,     2360295,      416370,       15625;
  7:   78125,   3180215,   27488205,    75698255,    75698255,    27488205,     3180215,      78125;
  8:  390625,  23745880,  301457500,  1245003880,  1968154630,  1245003880,   301457500,   23745880,    390625;
  9: 1953125, 174424285, 3164289220, 18819820180, 44261068390, 44261068390, 18819820180, 3164289220, 174424285, 1953125;
%F Formula
The row polynomials satisfy P(n,x) = (5+(2*n+3)*x)*P(n-1,x) + (2*x-2*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[(5 + (2*n + 3)*x)*P[n - 1, x] + (2*x - 2*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] = (5 + (2*n + 3)*x)*v[i - 1] + (2*x - 2*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.

A257615: reversed triangle, offset 0, from the row P0
%e Example
Triangle begins:
  0:       1;
  1:       5,         5;
  2:      25,        70,         25;
  3:     125,       715,        715,         125;
  4:     625,      6380,      12870,        6380,         625;
  5:    3125,     52785,     186010,      186010,       52785,        3125;
  6:   15625,    416370,    2360295,     4092220,     2360295,      416370,       15625;
  7:   78125,   3180215,   27488205,    75698255,    75698255,    27488205,     3180215,      78125;
  8:  390625,  23745880,  301457500,  1245003880,  1968154630,  1245003880,   301457500,   23745880,    390625;
  9: 1953125, 174424285, 3164289220, 18819820180, 44261068390, 44261068390, 18819820180, 3164289220, 174424285, 1953125;
%F Formula
Row n lists the coefficients of P(n,x) in descending powers of x, where P(n,x) = (5+(2*n+3)*x)*P(n-1,x) + (2*x-2*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[(5 + (2*n + 3)*x)*P[n - 1, x] + (2*x - 2*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] = (5 + (2*n + 3)*x)*v[i - 1] + (2*x - 2*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-e835bed38a18a979
  • 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-e835bed38a18a979
  • 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-e835bed38a18a979
  • 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-e835bed38a18a979

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