A257606 → Pₙ + Pₙ₊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:       5,        4;
  1:      20,       44,         16;
  2:      80,      336,        312,         64;
  3:     320,     2224,       3848,       1992,         256;
  4:    1280,    13616,      38360,      36736,       11944,        1024;
  5:    5120,    79344,     337160,     522120,      314040,       68680,        4096;
  6:   20480,   446896,    2725368,    6317312,     6132352,     2490672,      383336,      16384;
  7:   81920,  2455664,   20753512,   68447144,    99110000,    65040160,    18709736,    2092808,     65536;
  8:  327680, 13244976,  151154136,  684242112,  1403074296,  1372411440,   639955464,  134900064,  11234088,   262144;
  9: 1310720, 70419184, 1063788104, 6434059784, 18004398344, 24886091624, 17316229016, 5945258456, 942133016, 59512776, 1048576;

The row polynomials satisfy P(n,x) = (4+(n+2)*x)*P(n-2,x) + (x-x^2)*d/dx P(n-2,x) + (3+(n+4)*x)*P(n-1,x) + (x-x^2)*d/dx P(n-1,x) for n >= 2, with P(0,x) = 5 + 4*x, P(1,x) = 20 + 44*x + 16*x^2.

P[0, x_] := 5 + 4*x;
P[1, x_] := 20 + 44*x + 16*x^2;
P[n_, x_] := P[n, x] = Expand[(4 + (n + 2)*x)*P[n - 2, x] + (x - x^2)*D[P[n - 2, x], x] + (3 + (n + 4)*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] = 5 + 4*x; v[2] = 20 + 44*x + 16*x^2; for(n = 2, N, my(i = n + 1); v[i] = (4 + (n + 2)*x)*v[i - 2] + (x - x^2)*deriv(v[i - 2], x) + (3 + (n + 4)*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)

Proved properties

• Real-rooted. Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, +inf)
  Every polynomial of the sequence has only real roots, inside the stated interval.
  by the cited steps: e-7b496eddb4982c99

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

• obreschkoff_combination e-7b496eddb4982c99

  Hermite–Kakeya–Obreschkoff theorem [Obr63; Fis06, Thm 1.43] ?

  • premise (sequence): Triangle read by rows: T(n,k) = t(n-k, k); t(n,m) = f(m)*t(n-1,m) + f(n)*t(n,m-1), where f(x) = x + 4.
    uses: Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, +inf)
    • theorem_check liu_wang e-de9fa36753ad8047 root: theorem check

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

  • premise (sequence): Triangle read by rows: T(n,k) = t(n-k, k); t(n,m) = f(m)*t(n-1,m) + f(n)*t(n,m-1), where f(x) = x + 4.
    uses: Rows P_(m-1), P_m interlace (weak, unordered) for every m >= 1
    no recorded property covers this requirement

Related sequences ?

No candidate equalities or related sequences.

References

1. [Fis06] Steve Fisk. Polynomials, roots, and interlacing. arXiv:math/0612833. arXiv
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. [Obr63] Nikola Obreschkoff. Verteilung und berechnung der nullstellen reeller polynome. Hochschulbücher für mathematik, VEB Deutscher Verlag der Wissenschaften, 1963.