A161198 → basis A013609 → D+1

Matches ?

No OEIS matches.

Submission text ?

Triangle begins:
   1:          1;
   2:          7,           4;
   3:         47,          64,          16;
   4:        389,         764,         432,          64;
   5:       3921,        9568,        7904,        2560,         256;
   6:      46911,      132836,      138400,       65920,       14080,       1024;
   7:     651423,     2060576,     2523184,     1530880,      482560,      73728,      4096;
   8:   10311885,    35579484,    49178640,    35390656,    14309120,    3232768,    372736,     16384;
   9:  183410145,   679238208,  1032944064,   845730816,   408364544,  118931456,  20299776,   1835008,   65536;
  10: 3622630455, 14234969412, 23403465024, 21224395520, 11731646976, 4101888000, 905920512, 121307136, 8847360, 262144;

The row polynomials satisfy P(n,x) = -(4*n^2-12*n+9+(16*n-24)*x+16*x^2)*P(n-2,x) + (4*n-4+8*x)*P(n-1,x) for n >= 3, with P(1,x) = 1, P(2,x) = 7 + 4*x.

P[1, x_] := 1;
P[2, x_] := 7 + 4*x;
P[n_, x_] := P[n, x] = Expand[-(4*n^2 - 12*n + 9 + (16*n - 24)*x + 16*x^2)*P[n - 2, x] + (4*n - 4 + 8*x)*P[n - 1, x]];
Table[CoefficientList[P[n, x], x], {n, 1, 10}] // Flatten

P(N) = {my(v = vector(N)); v[1] = 1; v[2] = 7 + 4*x; for(n = 3, N, my(i = n); v[i] = -(4*n^2 - 12*n + 9 + (16*n - 24)*x + 16*x^2)*v[i - 2] + (4*n - 4 + 8*x)*v[i - 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)

Properties

• Real-rooted? Every row P_n, n ≥ 1, 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 ≥ 1: the coefficients of P_n have one sign
  derived from Laguerre’s theorem on differential operators
• Hadamard kernel (Malo)? Rows P_n, n ≥ 1, 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 ≥ 2
  by Laguerre’s theorem on differential operators

Proof chains ? JSON

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

  • from basis_map_A013609 of Triangle of polynomial coefficients related to the series expansions of (1-x)^((-1-2*n)/2).?
    • Geometric basis map (elementary) polytool ? step ›

      • from Triangle of polynomial coefficients related to the series expansions of (1-x)^((-1-2*n)/2).?
        • Liu–Wang theorem [LW07, Thm 2.1, Cor 2.4] ? step › direct check
        • 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
    • Geometric basis map (elementary) polytool ? step ›

      • from Triangle of polynomial coefficients related to the series expansions of (1-x)^((-1-2*n)/2).?
        • ↑ Liu–Wang theorem (above)
        • ↑ Parent-row provers of polytool (above)
        • ↑ Iterated real-rootedness preservers (above)

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.