Real-rooted atlas

A274498 → Veronese 2

nonnegative coefficients

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

Recurrence
\(P_{n}(x) = \left(6\right)\,P_{n-2}(x) + \left(-9 + 36\,x\right)\,P_{n-4}(x)\)
\(P_{0}(x) = 1\)
\(P_{1}(x) = 3\)
\(P_{2}(x) = 3\)
\(P_{3}(x) = 9\)

Rows ?

nx0x1Pn(1)
011
133
233
399
493645
527108135
627324351
7819721053

Show all 15 stored rows

Computed in your browser ?

Technical details
Node id
n-f130dfa84b5b7ad4 · revision 1 · JSON
Definition source
derived:veronese_section_2_0
Fingerprint
f6-6d8c58feedc3c04c

Observed on the stored rows ?

  • Degrees: 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3 (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

OEIS matches ?

No OEIS matches.

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:   3;
  2:   3;
  3:   9;
  4:   9,   36;
  5:  27,  108;
  6:  27,  324;
  7:  81,  972;
  8:  81, 1944, 1296;
  9: 243, 5832, 3888;
%F Formula
The row polynomials satisfy P(n,x) = 6*P(n-2,x) - (9-36*x)*P(n-4,x) for n >= 4, with P(0,x) = 1, P(1,x) = 3, P(2,x) = 3, P(3,x) = 9.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 3;
P[2, x_] := 3;
P[3, x_] := 9;
P[n_, x_] := P[n, x] = Expand[6*P[n - 2, x] - (9 - 36*x)*P[n - 4, 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] = 3; v[4] = 9; for(n = 4, N, my(i = n + 1); v[i] = 6*v[i - 2] - (9 - 36*x)*v[i - 4]); 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.

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-7469d4fe37c5c433
  • 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-7469d4fe37c5c433
  • 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-7469d4fe37c5c433

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

Same fingerprint (1)

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