A144698 → Pₙ + Pₙ₊₁

nonnegative coefficients

Proved for all n: all roots real what this means

Recurrence

\(P_{n}(x) = \left(1 + 2\,x + n x\right)\,P_{n-2}(x) + \left(x - x^{2}\right)\,P_{n-2}'(x) + \left(4\,x + n x\right)\,P_{n-1}(x) + \left(x - x^{2}\right)\,P_{n-1}'(x)\)

\(P_{0}(x) = 2 + 4\,x\)

\(P_{1}(x) = 2 + 17\,x + 16\,x^{2}\)

Rows ?

n	x⁰	x¹	x²	x³	x⁴	x⁵	x⁶	x⁷	x⁸	P_n(1)
0	2	4								6
1	2	17	16							35
2	2	45	129	64						240
3	2	103	644	885	256					1890
4	2	221	2621	7291	5641	1024				16800
5	2	459	9560	46980	71130	34093	4096			166320
6	2	937	32661	262310	678040	625953	198113	16384		1814400
7	2	1895	107044	1335719	5448170	8436253	5109440	1117541	65536	21621600

Show all 15 stored rows

Computed in your browser ?

Technical details

Node id: n-270e03b154c7e6f1 · revision 1 · JSON
Definition source: derived:obreschkoff_combination
Fingerprint: f6-a2b2cc17d6db6382

Observed on the stored rows ?

Degrees: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 (affine: slope 1, intercept 1)
Palindromic rows: no
γ-positive (gamma_positive): no
Nonnegative coefficients (nonn): yes
Only rational roots (rr_by_factors: every nonzero row is a product of linear factors over ℚ): no

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.

The atlas's own rows: n = 0, …, ascending powers of x

%e Example

Triangle begins:
  0: 2,    4;
  1: 2,   17,      16;
  2: 2,   45,     129,       64;
  3: 2,  103,     644,      885,       256;
  4: 2,  221,    2621,     7291,      5641,      1024;
  5: 2,  459,    9560,    46980,     71130,     34093,       4096;
  6: 2,  937,   32661,   262310,    678040,    625953,     198113,     16384;
  7: 2, 1895,  107044,  1335719,   5448170,   8436253,    5109440,   1117541,     65536;
  8: 2, 3813,  341349,  6388125,  39040521,  93590583,   94226967,  39402951,   6161145,   262144;
  9: 2, 7651, 1068536, 29225486, 257969936, 908072312, 1400470064, 969896954, 290766854, 33361629, 1048576;

%F Formula

The row polynomials satisfy P(n,x) = (1+(n+2)*x)*P(n-2,x) + (x-x^2)*d/dx P(n-2,x) + (n+4)*x*P(n-1,x) + (x-x^2)*d/dx P(n-1,x) for n >= 2, with P(0,x) = 2 + 4*x, P(1,x) = 2 + 17*x + 16*x^2.

%t Mathematica

P[0, x_] := 2 + 4*x;
P[1, x_] := 2 + 17*x + 16*x^2;
P[n_, x_] := P[n, x] = Expand[(1 + (n + 2)*x)*P[n - 2, x] + (x - x^2)*D[P[n - 2, x], x] + (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

%o PARI/GP

P(N) = {my(v = vector(N + 1)); v[1] = 2 + 4*x; v[2] = 2 + 17*x + 16*x^2; for(n = 2, N, my(i = n + 1); v[i] = (1 + (n + 2)*x)*v[i - 2] + (x - x^2)*deriv(v[i - 2], x) + (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)

Generated with polytool c48629374597.

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-7228e7730f21eb4a

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-7228e7730f21eb4a

Hermite–Kakeya–Obreschkoff theorem [Obr63; Fis06, Thm 1.43] ?
- premise (sequence): Triangle of 4-Eulerian numbers.
  uses: Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, +inf)
  - theorem_check liu_wang e-f86b9381645a3db7 root: theorem check
    
    Liu–Wang theorem [LW07, Thm 2.1, Cor 2.4] ?
- premise (sequence): Triangle of 4-Eulerian numbers.
  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

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