Stirling2 triangle with scaled diagonals (powers of 8).

OEIS matches ?

• A075507: row sums, 15 terms agree OEIS nonn (row-sum match: finite agreement only) · view at the OEIS

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:         64,            24,              1;
  1:        512,           448,             48,              1;
  2:       4096,          7680,           1600,             80,             1;
  3:      32768,        126976,          46080,           4160,           120,            1;
  4:     262144,       2064384,        1232896,         179200,          8960,          168,           1;
  5:    2097152,      33292288,       31653888,        6967296,        537600,        17024,         224,         1;
  6:   16777216,     534773760,      792985600,      254607360,      28471296,      1354752,       29568,       288,        1;
  7:  134217728,    8573157376,    19566428160,     8940421120,    1393459200,     93499392,     3010560,     48000,      360,      1;
  8: 1073741824,  137304735744,   478167433216,   305659904000,   64678789120,   5881430016,   262090752,   6082560,    73920,    440,   1;
  9: 8589934592, 2197949513728, 11613323132928, 10259284361216, 2892811468800, 346987429888, 20558512128, 651374592, 11404800, 109120, 528, 1;

The row polynomials satisfy P(n,x) = (8+x)*P(n-1,x) + 8*x*d/dx P(n-1,x) for n >= 1, with P(0,x) = 64 + 24*x + x^2.

P[0, x_] := 64 + 24*x + x^2;
P[n_, x_] := P[n, x] = Expand[(8 + x)*P[n - 1, x] + 8*x*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] = 64 + 24*x + x^2; for(n = 1, N, my(i = n + 1); v[i] = (8 + x)*v[i - 1] + 8*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 - 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-c4869f0cf2b30feb
• 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-c4869f0cf2b30feb
• 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-c4869f0cf2b30feb
• 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-c4869f0cf2b30feb
• Basis map preserves real-rootedness. Basis map u^k -> P_k sends roots in (-inf, 8] to roots in (-inf, 0]: source (-inf, a + b h + kappa m] = (-inf, 8] with m = 0, target (-inf, 0]
  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-c6b679d010c426c5

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-c6b679d010c426c5 root: theorem check

  Ray basis map theorem [MW08, Thm 2] polytool RealRooted rayBasisMap_maps_realRootedIn_iff ?

• theorem_check liu_wang e-c4869f0cf2b30feb root: theorem check

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

Used in 2 proof steps

• e-2d4f988e0d40946e obreschkoff_combination → obreschkoff_combination of Stirling2 triangle with scaled diagonals (powers of 8).
• e-2d4f988e0d40946e obreschkoff_combination → obreschkoff_combination of Stirling2 triangle with scaled diagonals (powers of 8).

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. [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