A322944: Coefficients of a family of orthogonal polynomials. Triangle read by rows, T(n, k) for 0 <= k <= n.

OEIS matches ?

• A322944: 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 = 0 ?
• A322943: row sums, 15 terms agree OEIS nonn (row-sum match: finite agreement only) · view at the OEIS · generated b-file 200 terms from n = 0 ?

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:
   1:      1;
   2:      1,        1;
   3:      2,        6,        1;
   4:      6,       38,       15,        1;
   5:     24,      272,      188,       28,        1;
   6:    120,     2200,     2340,      580,       45,       1;
   7:    720,    19920,    30280,    11040,     1390,      66,      1;
   8:   5040,   199920,   413560,   206920,    37450,    2842,     91,    1;
   9:  40320,  2204160,  5989760,  3931200,   955920,  102816,   5208,  120,   1;
  10: 362880, 26490240, 92050560, 76751360, 24005520, 3423504, 243432, 8808, 153, 1;

The row polynomials satisfy P(n,x) = (n-1+x)*P(n-1,x) + 3*x*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[(n - 1 + x)*P[n - 1, x] + 3*x*D[P[n - 1, x], x]];
Table[CoefficientList[P[n, x], x], {n, 1, 10}] // Flatten

P(N) = {my(v = vector(N)); v[1] = 1; for(n = 2, N, my(i = n); v[i] = (n - 1 + x)*v[i - 1] + 3*x*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, v[i])))};
T(10)

Triangle begins:
  0:      1;
  1:      1,        1;
  2:      2,        6,        1;
  3:      6,       38,       15,        1;
  4:     24,      272,      188,       28,        1;
  5:    120,     2200,     2340,      580,       45,       1;
  6:    720,    19920,    30280,    11040,     1390,      66,      1;
  7:   5040,   199920,   413560,   206920,    37450,    2842,     91,    1;
  8:  40320,  2204160,  5989760,  3931200,   955920,  102816,   5208,  120,   1;
  9: 362880, 26490240, 92050560, 76751360, 24005520, 3423504, 243432, 8808, 153, 1;

The row polynomials satisfy P(n,x) = (n+x)*P(n-1,x) + 3*x*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[(n + x)*P[n - 1, x] + 3*x*D[P[n - 1, x], x]];
Table[PadRight[CoefficientList[P[n, x], x], n + 1], {n, 0, 9}] // Flatten

P(N) = {my(v = vector(N + 1)); v[1] = 1; for(n = 1, N, my(i = n + 1); v[i] = (n + x)*v[i - 1] + 3*x*deriv(v[i - 1], x)); v};
row(n, p) = {my(c = Vecrev(p)); c = concat(c, vector(n + 1 - #c)); 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 >= 1, 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-d88ecdfd26f75232
• Coefficients of one sign. Every nonzero row, n >= 1: 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-d88ecdfd26f75232
• Hadamard kernel (Malo). Rows P_n, n >= 1, 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-d88ecdfd26f75232
• Interlacing of consecutive rows. Rows P_(m-1), P_m interlace (weak, previous interlaces next) for every m >= 2
  The roots of consecutive polynomials alternate on the real line.
  by the cited steps: e-d88ecdfd26f75232
• Basis map preserves real-rootedness. Basis map u^k -> P_k sends roots in (-inf, 0] to roots in (-inf, 0]: (-inf, 0] -> (-inf, 0] through R_s, s = 1, and U_g
  The linear map sending x^k to the k-th polynomial of the sequence turns polynomials with roots in one interval into real-rooted ones.
  by the cited steps: e-7c3b3334d944cc5f

Proof chains

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

• basis_map_theorem e-7c3b3334d944cc5f root: theorem check

  Index-dependent basis map [Bre89, Thm 2.4.3; MW08, Thm 2] polytool RealRooted basisMap_factorization_of_scalarIndex_recurrence RealRooted rayBasisMap_maps_realRootedIn_iff ?

• theorem_check liu_wang e-d88ecdfd26f75232 root: theorem check

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

Used in 2 proof steps

• e-11c2cb91bf9b2413 obreschkoff_combination → obreschkoff_combination of Coefficients of a family of orthogonal polynomials. Triangle r…
• e-11c2cb91bf9b2413 obreschkoff_combination → obreschkoff_combination of Coefficients of a family of orthogonal polynomials. Triangle r…

Related sequences ?

No candidate equalities or related sequences.

References

1. [Bre89] Francesco Brenti. Unimodal, log-concave and Pólya frequency sequences in combinatorics. Mem. Amer. Math. Soc., 81(413):viii+106, 1989. doi:10.1090/memo/0413
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. [MW08] Shi-Mei Ma and Yi Wang. q-Eulerian polynomials and polynomials with only real zeros. The Electronic Journal of Combinatorics, 15(1):Research Paper 17, January 2008. doi:10.37236/741