A038271 → basis A013609 → (θ+1)²

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Submission text ?

Triangle begins:
  0:          1;
  1:         12,           40;
  2:        144,          960,           900;
  3:       1728,        17280,         32400,         16000;
  4:      20736,       276480,        777600,        768000,        250000;
  5:     248832,      4147200,      15552000,      23040000,      15000000,       3600000;
  6:    2985984,     59719680,     279936000,     552960000,     540000000,     259200000,      49000000;
  7:   35831808,    836075520,    4702924800,   11612160000,   15120000000,   10886400000,    4116000000,     640000000;
  8:  429981696,  11466178560,   75246796800,  222953472000,  362880000000,  348364800000,  197568000000,   61440000000,   8100000000;
  9: 5159780352, 154793410560, 1160950579200, 4013162496000, 7838208000000, 9405849600000, 7112448000000, 3317760000000, 874800000000, 100000000000;

The row polynomials satisfy (36+(90*n-30)*x+25*n^2*x^2)*P(n,x) = (432+(1080*n+1080)*x+(300*n^2+1500*n+900)*x^2+(250*n^2+500*n+250)*x^3)*P(n-1,x) for n >= 1, with P(0,x) = 1.

P[0, x_] := 1;
P[n_, x_] := P[n, x] = Expand[Together[((432 + (1080*n + 1080)*x + (300*n^2 + 1500*n + 900)*x^2 + (250*n^2 + 500*n + 250)*x^3)*P[n - 1, x])/(36 + (90*n - 30)*x + 25*n^2*x^2)]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten

P(N) = {my(v = vector(N + 1)); v[1] = 1; for(n = 1, N, my(i = n + 1); v[i] = ((432 + (1080*n + 1080)*x + (300*n^2 + 1500*n + 900)*x^2 + (250*n^2 + 500*n + 250)*x^3)*v[i - 1])/(36 + (90*n - 30)*x + 25*n^2*x^2)); 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)

Properties

• Real-rooted? Every row P_n, n ≥ 0, is zero or real-rooted with all roots in (−∞, 0]
  by Laguerre’s theorem on multiplier sequences
• Coefficients of one sign? Every nonzero row, n ≥ 0: the coefficients of P_n have one sign
  derived from Laguerre’s theorem on multiplier sequences
• Hadamard kernel (Malo)? Rows P_n, n ≥ 0, are Hadamard kernels (preserve real-rootedness)
  derived from Laguerre’s theorem on multiplier sequences
• Interlacing of consecutive rows? Rows P_(m-1), P_m interlace (weak, unordered) for every m ≥ 1
  by Laguerre’s theorem on multiplier sequences

Proof chains ? JSON

• Laguerre’s theorem on multiplier sequences [SP14; Bra15, Thm 7.1 of arXiv:1410.6601] polytool ? step ›

  • from basis_map_A013609 of Triangle whose (i,j)-th entry is binomial(i,j)*7^(i-j)*5^j.?
    • Geometric basis map (elementary) polytool ? step ›

      • from Triangle whose (i,j)-th entry is binomial(i,j)*7^(i-j)*5^j.?
        • Row-hypergeometric rows (multiplier sequences) [SP14; Bra15, Thm 7.1 of arXiv:1410.6601] polytool RealRooted RealRooted.isPFMultiplierSequence_eval_of_roots_nonpos RealRooted RealRooted.isPFMultiplierSequence_inv_ascPochhammer RealRooted RealRooted.IsPFMultiplierSequence.mul ? step › direct check
        • Liu–Wang theorem [LW07, Thm 2.1, Cor 2.4] ? step › direct check
        • Iterated real-rootedness preservers [SP14; Bra15, Thm 7.1 of arXiv:1410.6601; Bra06, Cor 3.5] polytool ? step › direct check
        • Parent-row provers of polytool polytool ? step › direct check

Related ?

Same fingerprint ?

• A013612 → x ↦ x+1 → (θ+1)²
• A038336 → (θ+1)²
• A038259 → (θ+1)²

References

1. [Bra06] Petter Brändén. On linear transformations preserving the Pólya frequency property. Transactions of the American Mathematical Society, 358(8):3697–3716, February 2006. doi:10.1090/s0002-9947-06-03856-6
2. [Bra15] Petter Brändén. Unimodality, log-concavity, real-rootedness and beyond. Handbook of enumerative combinatorics, :437–483, March 2015. doi:10.1201/b18255-10
3. [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
4. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.