A178820 → Veronese 2 → D+1

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Submission text ?

Triangle begins:
  0:    1;
  1:    4;
  2:   20,    10;
  3:   80,    60;
  4:  245,   280,    35;
  5:  616,  1120,   280;
  6: 1344,  3780,  1512,    84;
  7: 2640, 10920,  6720,   840;
  8: 4785, 27720, 25410,  5280,  165;
  9: 8140, 63360, 83160, 26400, 1980;

The row polynomials satisfy (n^4-4*n^3+7*n^2-4*n+(4*n^3-18*n^2+14*n)*x+(4*n^2-4*n)*x^2)*P(n,x) = (n^4+n^3-3*n^2+7*n-6+(n^4+3*n^3-17*n^2-35*n+48)*x+(4*n^3+2*n^2-24*n+18)*x^2+(4*n^2+8*n-12)*x^3)*P(n-1,x) + ((2*n^3+4*n^2-10*n-12)*x-(2*n^3-4*n^2-22*n+24)*x^2-(8*n^2+4*n-60)*x^3-(8*n+24)*x^4)*d/dx P(n-1,x) for n >= 2, with P(0,x) = 1, P(1,x) = 4.

P[0, x_] := 1;
P[1, x_] := 4;
P[n_, x_] := P[n, x] = Expand[Together[((n^4 + n^3 - 3*n^2 + 7*n - 6 + (n^4 + 3*n^3 - 17*n^2 - 35*n + 48)*x + (4*n^3 + 2*n^2 - 24*n + 18)*x^2 + (4*n^2 + 8*n - 12)*x^3)*P[n - 1, x] + ((2*n^3 + 4*n^2 - 10*n - 12)*x - (2*n^3 - 4*n^2 - 22*n + 24)*x^2 - (8*n^2 + 4*n - 60)*x^3 - (8*n + 24)*x^4)*D[P[n - 1, x], x])/(n^4 - 4*n^3 + 7*n^2 - 4*n + (4*n^3 - 18*n^2 + 14*n)*x + (4*n^2 - 4*n)*x^2)]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten

P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 4; for(n = 2, N, my(i = n + 1); v[i] = ((n^4 + n^3 - 3*n^2 + 7*n - 6 + (n^4 + 3*n^3 - 17*n^2 - 35*n + 48)*x + (4*n^3 + 2*n^2 - 24*n + 18)*x^2 + (4*n^2 + 8*n - 12)*x^3)*v[i - 1] + ((2*n^3 + 4*n^2 - 10*n - 12)*x - (2*n^3 - 4*n^2 - 22*n + 24)*x^2 - (8*n^2 + 4*n - 60)*x^3 - (8*n + 24)*x^4)*deriv(v[i - 1], x))/(n^4 - 4*n^3 + 7*n^2 - 4*n + (4*n^3 - 18*n^2 + 14*n)*x + (4*n^2 - 4*n)*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 differential operators
• Coefficients of one sign? Every nonzero row, n ≥ 0: the coefficients of P_n have one sign
  derived from Laguerre’s theorem on differential operators
• Hadamard kernel (Malo)? Rows P_n, n ≥ 0, are Hadamard kernels (preserve real-rootedness)
  derived from Laguerre’s theorem on differential operators

Proof chains ? JSON

• Laguerre’s theorem on differential operators [SP14] polytool ? step ›

  • from veronese_section_2_0 of Triangle read by rows: T(n,k) = C(n+3,3) * C(n,k), 0 <= k <= n.?
    • Veronese sections of Pólya frequency sequences [ASW52; Edr53; AW24] polytool ? step ›

      • from Triangle read by rows: T(n,k) = C(n+3,3) * C(n,k), 0 <= k <= n.?
        • Liu–Wang theorem [LW07, Thm 2.1, Cor 2.4] ? step › direct check
        • 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
        • Affine, reversal and Möbius substitutions (elementary) polytool ? step ›

          • from Triangle read by rows: T(n,k) = C(n+3,3) * C(n,k), 0 <= k <= n.?
            • ↑ Liu–Wang theorem (above)
            • ↑ Row-hypergeometric rows (multiplier sequences) (above)
            • Affine, reversal and Möbius substitutions (elementary) polytool ? step ›

              • from Triangle read by rows: T(n,k) = C(n+3,3) * C(n,k), 0 <= k <= n.?
                • ↑ Liu–Wang theorem (above)
                • ↑ Row-hypergeometric rows (multiplier sequences) (above)
                • Iterated real-rootedness preservers [SP14; Bra15, Thm 7.1 of arXiv:1410.6601; Bra06, Cor 3.5] polytool ? step › direct check
            • ↑ Iterated real-rootedness preservers (above)
        • ↑ Affine, reversal and Möbius substitutions (elementary) (above)
        • ↑ Iterated real-rootedness preservers (above)

Related ?

Same fingerprint ?

• basis-map coefficients of A113214, shifted → Veronese 2 → D+1
• A038208 → Veronese 2 → D+1
• A034839 → D+1
• A003506 → Veronese 2 → D+1
• A028326 → Veronese 2 → D+1
• A119462 → D+1
• A178821 → Veronese 2 → D+1
• A228955 → D+1
• A178822 → Veronese 2 → D+1

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. [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
4. [Bra15] Petter Brändén. Unimodality, log-concavity, real-rootedness and beyond. Handbook of enumerative combinatorics, :437–483, March 2015. doi:10.1201/b18255-10
5. [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
6. [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
7. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.