A055356 → D+1

OEIS matches ?

No OEIS matches.

OEIS submission text ?

Fields to paste into an OEIS submission: the example %e, the formula %F and programs %t (Mathematica) and %o (PARI/GP) that list the same rows. For an OEIS link the row numbers, the offset and the orientation are those of the entry, as matched; the matched terms were compared with the published ones, which identifies the node with the entry on a finite prefix, not for every n. The PARI/GP program is not machine-checked here.

Triangle begins:
  0:   1;
  1:   1;
  2:   2,     1;
  3:   5,     8,      2;
  4:  12,    47,     36,       6;
  5:  27,   222,    386,     192,      24;
  6:  58,   905,   3046,    3274,    1200,     120;
  7: 121,  3348,  19734,   39016,   29844,    8640,     720;
  8: 248, 11611, 112056,  369458,  501640,  295308,   70560,   5040;
  9: 503, 38546, 580886, 2991944, 6550004, 6665672, 3173904, 645120, 40320;

The row polynomials satisfy (n-3)*P(n,x) = -(2*n-4+(2*n^2-9*n+10)*x+(n^3-7*n^2+16*n-12)*x^2)*P(n-2,x) - ((n-2)*x+(n^2-5*n+6)*x^2)*d/dx P(n-2,x) + (3*n-8+(2*n^2-9*n+9)*x)*P(n-1,x) + (n-3)*x*d/dx P(n-1,x) for n >= 4, with P(0,x) = 1, P(1,x) = 1, P(2,x) = 2 + x, P(3,x) = 5 + 8*x + 2*x^2.

P[0, x_] := 1;
P[1, x_] := 1;
P[2, x_] := 2 + x;
P[3, x_] := 5 + 8*x + 2*x^2;
P[n_, x_] := P[n, x] = Expand[Together[(-(2*n - 4 + (2*n^2 - 9*n + 10)*x + (n^3 - 7*n^2 + 16*n - 12)*x^2)*P[n - 2, x] - ((n - 2)*x + (n^2 - 5*n + 6)*x^2)*D[P[n - 2, x], x] + (3*n - 8 + (2*n^2 - 9*n + 9)*x)*P[n - 1, x] + (n - 3)*x*D[P[n - 1, x], x])/(n - 3)]];
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; v[4] = 5 + 8*x + 2*x^2; for(n = 4, N, my(i = n + 1); v[i] = (-(2*n - 4 + (2*n^2 - 9*n + 10)*x + (n^3 - 7*n^2 + 16*n - 12)*x^2)*v[i - 2] - ((n - 2)*x + (n^2 - 5*n + 6)*x^2)*deriv(v[i - 2], x) + (3*n - 8 + (2*n^2 - 9*n + 9)*x)*v[i - 1] + (n - 3)*x*deriv(v[i - 1], x))/(n - 3)); 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)

Proved properties

• Real-rooted. Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, 0]
  Every polynomial of the sequence has only real roots, inside the stated interval.
  by the cited steps: e-a4a74e2992ffd908
• Coefficients of one sign. Every nonzero row, n >= 0: the coefficients of P_n have one sign
  All coefficients of each polynomial have the same sign (after x -> -x when alternating).
  derived from the cited steps by a stated theorem: e-a4a74e2992ffd908
• Hadamard kernel (Malo). Rows P_n, n >= 0, are Hadamard kernels (preserve real-rootedness)
  Multiplying the coefficients of any real-rooted polynomial termwise by those of a row (Hadamard product) gives a real-rooted polynomial again.
  derived from the cited steps by a stated theorem: e-a4a74e2992ffd908
• Interlacing of consecutive rows. Rows P_(m-1), P_m interlace (weak, unordered) for every m >= 1
  The roots of consecutive polynomials alternate on the real line.
  by the cited steps: e-a4a74e2992ffd908

Proof chains

1 incoming proof step. Each step is expanded back to the roots of the proof DAG, the theorem checks of a node's own rule. JSON

• preserver_image derivative_polynomial, shift 0 e-a4a74e2992ffd908

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

  • premise (sequence): Triangle of increasing mobiles (circular rooted trees) with n nodes and k leaves.
    uses: Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, 0]
    • theorem_check liu_wang e-b2d04b9d5c5e725d root: theorem check

      Liu–Wang theorem [LW07, Thm 2.1, Cor 2.4] ?

Related sequences ?

No candidate equalities or related sequences.

References

1. [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
2. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.