type_b_eulerian → γ (scale 1/4) → (θ+1)²

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: 1,     4;
  3: 1,    20;
  4: 1,    72,     45;
  5: 1,   232,    549;
  6: 1,   716,   4311,     976;
  7: 1,  2172,  27999,   22160;
  8: 1,  6544, 164430,  304448,   34625;
  9: 1, 19664, 910494, 3300416, 1263025;

The row polynomials satisfy n^2*P(n,x) = (n^2+n-(4*n^3-4*n^2-16*n+16)*x+(9*n^4-13*n^3-10*n^2)*x^2)*P(n-2,x) - ((4*n^2+4*n-6)*x-(4*n^3+20*n^2+20*n-20)*x^2-(4*n^4-32*n^3-18*n^2)*x^3)*d/dx P(n-2,x) - ((4*n^2+4*n-4)*x^2-(8*n^3+8*n^2+4*n-4)*x^3+(8*n^3+4*n^2)*x^4)*d^2/dx^2 P(n-2,x) - (n-(4*n^3-4*n^2)*x)*P(n-1,x) + ((4*n^2+2*n-2)*x-(4*n^3+4*n^2)*x^2)*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[((n^2 + n - (4*n^3 - 4*n^2 - 16*n + 16)*x + (9*n^4 - 13*n^3 - 10*n^2)*x^2)*P[n - 2, x] - ((4*n^2 + 4*n - 6)*x - (4*n^3 + 20*n^2 + 20*n - 20)*x^2 - (4*n^4 - 32*n^3 - 18*n^2)*x^3)*D[P[n - 2, x], x] - ((4*n^2 + 4*n - 4)*x^2 - (8*n^3 + 8*n^2 + 4*n - 4)*x^3 + (8*n^3 + 4*n^2)*x^4)*D[P[n - 2, x], {x, 2}] - (n - (4*n^3 - 4*n^2)*x)*P[n - 1, x] + ((4*n^2 + 2*n - 2)*x - (4*n^3 + 4*n^2)*x^2)*D[P[n - 1, x], 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; for(n = 2, N, my(i = n + 1); v[i] = ((n^2 + n - (4*n^3 - 4*n^2 - 16*n + 16)*x + (9*n^4 - 13*n^3 - 10*n^2)*x^2)*v[i - 2] - ((4*n^2 + 4*n - 6)*x - (4*n^3 + 20*n^2 + 20*n - 20)*x^2 - (4*n^4 - 32*n^3 - 18*n^2)*x^3)*deriv(v[i - 2], x) - ((4*n^2 + 4*n - 4)*x^2 - (8*n^3 + 8*n^2 + 4*n - 4)*x^3 + (8*n^3 + 4*n^2)*x^4)*deriv(deriv(v[i - 2], x), x) - (n - (4*n^3 - 4*n^2)*x)*v[i - 1] + ((4*n^2 + 2*n - 2)*x - (4*n^3 + 4*n^2)*x^2)*deriv(v[i - 1], x))/(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)

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-1aee28e48ce84e67
• 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-1aee28e48ce84e67
• 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-1aee28e48ce84e67

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 euler_polynomial, shift 0 e-1aee28e48ce84e67

  Laguerre’s theorem on multiplier sequences [SP14; Bra15, Thm 40] polytool ?

  • premise (sequence): Triangle read by rows: T(n,k) is the number of permutations of [n] with k increasing runs of length at least 2.
    uses: Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, 0]
    • gamma_polynomial scale 1/4, shift 0 e-4c46966ead0b055f

      Gamma criterion RealRooted IsGammaExpansion.isRealRooted_and_hasRootsNonpos_iff ?

      • premise (sequence): type_b_eulerian
        uses: Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, 0]
        • theorem_check liu_wang e-4675d8b985e3f46a root: theorem check

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

Related sequences ?

No candidate equalities or related sequences.

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