A367270 → basis A013611 → θ+1

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Submission text ?

Triangle begins:
  0:     1;
  1:     1;
  2:     3,     16;
  3:    10,     96,     144;
  4:    35,    480,    1440,     1024;
  5:   126,   2240,   10080,    15360,      6400;
  6:   462,  10080,   60480,   143360,    134400,     36864;
  7:  1716,  44352,  332640,  1075200,   1612800,   1032192,    200704;
  8:  6435, 192192, 1729728,  7096320,  14784000,  15482880,   7225344,  1048576;
  9: 24310, 823680, 8648640, 43051008, 115315200, 170311680, 132464640, 47185920, 5308416;

The row polynomials satisfy (2*n^3-3*n^2+n+(4*n^4-8*n^3+4*n^2)*x)*P(n,x) = (8*n^3-16*n^2+10*n-2+(16*n^4+8*n^3-72*n^2+64*n-16)*x+(48*n^4-64*n^3-32*n^2+80*n-32)*x^2)*P(n-1,x) - ((4*n^2-4*n+1)*x+(8*n^3+16*n^2-24*n+8)*x^2+(32*n^3-32*n+16)*x^3)*d/dx P(n-1,x) for n >= 2, with P(0,x) = 1, P(1,x) = 1.

P[0, x_] := 1;
P[1, x_] := 1;
P[n_, x_] := P[n, x] = Expand[Together[((8*n^3 - 16*n^2 + 10*n - 2 + (16*n^4 + 8*n^3 - 72*n^2 + 64*n - 16)*x + (48*n^4 - 64*n^3 - 32*n^2 + 80*n - 32)*x^2)*P[n - 1, x] - ((4*n^2 - 4*n + 1)*x + (8*n^3 + 16*n^2 - 24*n + 8)*x^2 + (32*n^3 - 32*n + 16)*x^3)*D[P[n - 1, x], x])/(2*n^3 - 3*n^2 + n + (4*n^4 - 8*n^3 + 4*n^2)*x)]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten

P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 1; for(n = 2, N, my(i = n + 1); v[i] = ((8*n^3 - 16*n^2 + 10*n - 2 + (16*n^4 + 8*n^3 - 72*n^2 + 64*n - 16)*x + (48*n^4 - 64*n^3 - 32*n^2 + 80*n - 32)*x^2)*v[i - 1] - ((4*n^2 - 4*n + 1)*x + (8*n^3 + 16*n^2 - 24*n + 8)*x^2 + (32*n^3 - 32*n + 16)*x^3)*deriv(v[i - 1], x))/(2*n^3 - 3*n^2 + n + (4*n^4 - 8*n^3 + 4*n^2)*x)); 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 ≥ 2
  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_A013611 of Triangle read by rows. T(n, k) = binomial(n, k)*binomial(n - 1, n - k - 1).?
    • Geometric basis map (elementary) polytool ? step ›

      • from Triangle read by rows. T(n, k) = binomial(n, k)*binomial(n - 1, n - k - 1).?
        • Three-term recurrence criterion [Sze39, §3.3; Fav35] polytool ? 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
        • Liu–Wang theorem for three-term recurrences [LW07, Thm 2.1, Thm 2.3, Cor 2.4, Prop 3.3] polytool ? step › direct check
    • Geometric basis map (elementary) polytool ? step ›

      • from Triangle read by rows. T(n, k) = binomial(n, k)*binomial(n - 1, n - k - 1).?
        • ↑ Three-term recurrence criterion (above)
        • ↑ Row-hypergeometric rows (multiplier sequences) (above)
        • ↑ Liu–Wang theorem for three-term recurrences (above)

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. [Fav35] Jean Favard. Sur les polynômes de tchebicheff. C. R. Acad. Sci. Paris, 200:2052–2053, 1935.
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.
5. [Sze39] G. Szegő. Orthogonal Polynomials. Colloquium publications, American Mathematical Society, 1939. doi:10.1090/coll/023