A219512: Triangle of third-order Eulerian numbers: 3-Stirling permutations enumerated by ascents.

OEIS matches ?

• A007559: row sums, 15 terms agree OEIS nonn (row-sum match: finite agreement only) · view at the OEIS
• A219512: triangle, 45 terms agree, 9 full rows row-aligned (tabl) OEIS nonn in polytool catalog · view at the OEIS · generated b-file 990 terms from n = 1 ?

A generated b-file is computed from the node's definition along the row alignment of its OEIS link and starts at the entry's offset. It is an identification on a finite prefix, not a proof that the node and the OEIS entry agree for every n.

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,    3;
  2: 1,   12,     15;
  3: 1,   33,    141,      105;
  4: 1,   78,    786,     1830,       945;
  5: 1,  171,   3450,    17538,     26685,      10395;
  6: 1,  360,  13257,   125352,    396495,     435960,     135135;
  7: 1,  741,  46971,   753291,   4238811,    9356175,    7921305,    2027025;
  8: 1, 1506, 157956,  4046526,  37013166,  140913270,  233216460,  158799690,   34459425;
  9: 1, 3039, 513024, 20135004, 282182454, 1696782438, 4732607160, 6167943180, 3486128625, 654729075;

The row polynomials satisfy P(n,x) = (1+3*n*x)*P(n-1,x) + (x-x^2)*d/dx P(n-1,x) for n >= 1, with P(0,x) = 1.

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

P(N) = {my(v = vector(N + 1)); v[1] = 1; for(n = 1, N, my(i = n + 1); v[i] = (1 + 3*n*x)*v[i - 1] + (x - x^2)*deriv(v[i - 1], 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)

Triangle begins:
   1: 1;
   2: 1,    3;
   3: 1,   12,     15;
   4: 1,   33,    141,      105;
   5: 1,   78,    786,     1830,       945;
   6: 1,  171,   3450,    17538,     26685,      10395;
   7: 1,  360,  13257,   125352,    396495,     435960,     135135;
   8: 1,  741,  46971,   753291,   4238811,    9356175,    7921305,    2027025;
   9: 1, 1506, 157956,  4046526,  37013166,  140913270,  233216460,  158799690,   34459425;
  10: 1, 3039, 513024, 20135004, 282182454, 1696782438, 4732607160, 6167943180, 3486128625, 654729075;

The row polynomials satisfy P(n,x) = (1+(3*n-3)*x)*P(n-1,x) + (x-x^2)*d/dx P(n-1,x) for n >= 2, with P(1,x) = 1.

P[1, x_] := 1;
P[n_, x_] := P[n, x] = Expand[(1 + (3*n - 3)*x)*P[n - 1, x] + (x - x^2)*D[P[n - 1, x], x]];
Table[PadRight[CoefficientList[P[n, x], x], n], {n, 1, 10}] // Flatten

P(N) = {my(v = vector(N)); v[1] = 1; for(n = 2, N, my(i = n); v[i] = (1 + (3*n - 3)*x)*v[i - 1] + (x - x^2)*deriv(v[i - 1], x)); v};
row(n, p) = {my(c = Vecrev(p)); c = concat(c, vector(n - #c)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i, v[i])))};
T(10)

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-5be8dcded4b783ba
• 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-5be8dcded4b783ba
• 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-5be8dcded4b783ba
• Interlacing of consecutive rows. Rows P_(m-1), P_m interlace (weak, previous interlaces next) for every m >= 1
  The roots of consecutive polynomials alternate on the real line.
  by the cited steps: e-5be8dcded4b783ba

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

• theorem_check liu_wang e-5be8dcded4b783ba root: theorem check

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

Used in 2 proof steps

• e-b4f1d8e4113d9eff obreschkoff_combination → obreschkoff_combination of Triangle of third-order Eulerian numbers: 3-Stirling permutati…
• e-b4f1d8e4113d9eff obreschkoff_combination → obreschkoff_combination of Triangle of third-order Eulerian numbers: 3-Stirling permutati…

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