A132393 → reverse → D+1

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Submission text ?

Triangle begins:
  0:  1;
  1:  1;
  2:  2,    1;
  3:  4,    7,     2;
  4:  7,   28,    29,     6;
  5: 11,   80,   185,   146,     24;
  6: 16,  185,   760,  1321,    874,    120;
  7: 22,  371,  2380,  7231,  10444,   6084,    720;
  8: 29,  672,  6202, 29036,  72429,  91540,  48348,   5040;
  9: 37, 1128, 14154, 94332, 358869, 776028, 885212, 432144, 40320;

The row polynomials satisfy (n-2)*P(n,x) = -(n-1+(2*n^2-6*n+4)*x+(n^3-5*n^2+8*n-4)*x^2)*P(n-2,x) + (2*n-3+(2*n^2-6*n+4)*x)*P(n-1,x) for n >= 3, with P(0,x) = 1, P(1,x) = 1, P(2,x) = 2 + x.

P[0, x_] := 1;
P[1, x_] := 1;
P[2, x_] := 2 + x;
P[n_, x_] := P[n, x] = Expand[Together[(-(n - 1 + (2*n^2 - 6*n + 4)*x + (n^3 - 5*n^2 + 8*n - 4)*x^2)*P[n - 2, x] + (2*n - 3 + (2*n^2 - 6*n + 4)*x)*P[n - 1, x])/(n - 2)]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten

P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 1; v[3] = 2 + x; for(n = 3, N, my(i = n + 1); v[i] = (-(n - 1 + (2*n^2 - 6*n + 4)*x + (n^3 - 5*n^2 + 8*n - 4)*x^2)*v[i - 2] + (2*n - 3 + (2*n^2 - 6*n + 4)*x)*v[i - 1])/(n - 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
• Interlacing of consecutive rows? Rows P_(m-1), P_m interlace (weak, unordered) for every m ≥ 1
  by Laguerre’s theorem on differential operators

Proof chains ? JSON

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

  • from reversal of Triangle of unsigned Stirling numbers of the first kind (see A048994), read by rows, T(n,k) for 0 <= k <= n.?
    • Affine, reversal and Möbius substitutions (elementary) polytool ? step ›

      • from Triangle of unsigned Stirling numbers of the first kind (see A048994), read by rows, T(n,k) for 0 <= k <= n.?
        • Parent-row provers of polytool polytool ? 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
    • Affine, reversal and Möbius substitutions (elementary) polytool ? step ›

      • from Triangle of unsigned Stirling numbers of the first kind (see A048994), read by rows, T(n,k) for 0 <= k <= n.?
        • ↑ Parent-row provers of polytool (above)
        • ↑ Iterated real-rootedness preservers (above)
        • ↑ Parent-row provers of polytool (above)

Related ?

Same fingerprint ?

• A094638 → D+1 → reverse
• A094638 → D+1

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. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.