basis-map coefficients of A112227 → (θ+1)²

palindromic γ-positive nonnegative coefficients only rational roots

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

Recurrence
\(\left(1 + 2\,n + n^{2}\right)\,P_{n}(x) = \left(4\,x + 4\,n x + n^{2} x\right)\,P_{n-1}(x)\)
\(P_{1}(x) = 9\,x^{2}\)

Rows ?

nx0x1x2x3x4x5x6x7x8x9Pn(1)
10099
20001616
300002525
4000003636
50000004949
600000006464
7000000008181
8000000000100100

Computed in your browser ?

Technical details
Node id
n-efb24c96253c2b9d · revision 1 · JSON
Definition source
derived:theta_plus_one_squared
Fingerprint
f6-edf6954a4cd8adfc

Observed on the stored rows ?

  • Degrees: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 (affine: slope 1, intercept 1)
  • 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): yes

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 = 1, …, ascending powers of x
%e Example
Triangle begins:
   1: 0, 0, 9;
   2: 0, 0, 0, 16;
   3: 0, 0, 0,  0, 25;
   4: 0, 0, 0,  0,  0, 36;
   5: 0, 0, 0,  0,  0,  0, 49;
   6: 0, 0, 0,  0,  0,  0,  0, 64;
   7: 0, 0, 0,  0,  0,  0,  0,  0, 81;
   8: 0, 0, 0,  0,  0,  0,  0,  0,  0, 100;
   9: 0, 0, 0,  0,  0,  0,  0,  0,  0,   0, 121;
  10: 0, 0, 0,  0,  0,  0,  0,  0,  0,   0,   0, 144;
%F Formula
The row polynomials satisfy (n^2+2*n+1)*P(n,x) = (n^2+4*n+4)*x*P(n-1,x) for n >= 2, with P(1,x) = 9*x^2.
%t Mathematica
P[1, x_] := 9*x^2;
P[n_, x_] := P[n, x] = Expand[Together[((n^2 + 4*n + 4)*x*P[n - 1, x])/(n^2 + 2*n + 1)]];
Table[CoefficientList[P[n, x], x], {n, 1, 10}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N)); v[1] = 9*x^2; for(n = 2, N, my(i = n); v[i] = ((n^2 + 4*n + 4)*x*v[i - 1])/(n^2 + 2*n + 1)); v};
row(n, p) = {my(c = Vecrev(p)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i, v[i])))};
T(10)

Generated with polytool c48629374597.

Proved properties

  • Real-rooted. Every row P_n, n >= 1, 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-c527a11d264443d6
  • Coefficients of one sign. Every nonzero row, n >= 1: 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-c527a11d264443d6
  • Hadamard kernel (Malo). Rows P_n, n >= 1, 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-c527a11d264443d6

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 (75)

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

References

  1. [Bra15] Petter Brändén. Unimodality, log-concavity, real-rootedness and beyond. Handbook of enumerative combinatorics, :437–483, March 2015. doi:10.1201/b18255-10
  2. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.