Real-rooted atlas

A102547 → x ↦ (1/27)x → basis A007318 → x ↦ x+1

nonnegative coefficients

Proved for all n all roots real, in (−∞, −1]coefficients of one signHadamard kernel

Recurrence

\(P_{n}(x) = \left(2 + x\right)\,P_{n-3}(x) + \left(3\right)\,P_{n-1}(x)\)
\(P_{0}(x) = 1\)
\(P_{1}(x) = 3\)
\(P_{2}(x) = 9\)

Rows ?

nx0x1x2Pn(1)
011
133
299
329130
493699
529727324
694911211062
7303344193483

All 15 rows

Technical details
Node id
n-b2edf0853b168590 · revision 0 · JSON
Definition source
derived:shift_x_plus_one
Fingerprint
f6-d2508ec99031e8ea

Observed on the stored rows ?

  • Degrees: 0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4 (irregular)
  • 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

Matches ?

No OEIS matches.

Submission text ?

Atlas rows n = 0, …, ascending powers of x
%e Example
Triangle begins:
  0:     1;
  1:     3;
  2:     9;
  3:    29,    1;
  4:    93,    6;
  5:   297,   27;
  6:   949,  112,   1;
  7:  3033,  441,   9;
  8:  9693, 1674,  54;
  9: 30977, 6195, 276, 1;
%F Formula
The row polynomials satisfy P(n,x) = (2+x)*P(n-3,x) + 3*P(n-1,x) for n >= 3, with P(0,x) = 1, P(1,x) = 3, P(2,x) = 9.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 3;
P[2, x_] := 9;
P[n_, x_] := P[n, x] = Expand[(2 + x)*P[n - 3, x] + 3*P[n - 1, 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] = 3; v[3] = 9; for(n = 3, N, my(i = n + 1); v[i] = (2 + x)*v[i - 3] + 3*v[i - 1]); 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)

polytool c48629374597

Properties

Proof chains ? JSON