A119462 → θ+1

nonnegative coefficients

Proved for all n all roots real, in (−∞, 0]coefficients of one sign Hadamard kernel

Recurrence

\(\left(6 - 6\,n - n x + n^{3} x\right)\,P_{n}(x) = \left(6 + 12\,x - 2\,x^{2} - 6\,n - 13\,n x - n x^{2} + 2\,n^{2} x^{2} + n^{3} x + n^{3} x^{2}\right)\,P_{n-1}(x) + \left(-12\,x + 16\,x^{2} - 4\,x^{3} + 6\,n x^{2} - 6\,n x^{3} + 2\,n^{2} x^{2} - 2\,n^{2} x^{3}\right)\,P_{n-1}'(x)\)

\(P_{0}(x) = 1\)

\(P_{1}(x) = 2\)

Rows ?

n	x⁰	x¹	x²	x³	P_n(1)
0	1				1
1	2				2
2	2	4			6
3	2	12			14
4	2	24	6		32
5	2	40	30		72
6	2	60	90	8	160
7	2	84	210	56	352

All 15 rows

Technical details

Node id: n-fe6d1525fb9fff85 · revision 0 · JSON
Definition source: derived:theta_plus_one
Fingerprint: f6-9ad63b3855519f4d

Observed on the stored rows ?

Degrees: 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7 (half affine: slope 1, intercept 0)
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

Matches ?

No OEIS matches.

Submission text ?

Atlas rows n = 0, …, ascending powers of x

%e Example

Triangle begins:
  0: 1;
  1: 2;
  2: 2,   4;
  3: 2,  12;
  4: 2,  24,   6;
  5: 2,  40,  30;
  6: 2,  60,  90,   8;
  7: 2,  84, 210,  56;
  8: 2, 112, 420, 224, 10;
  9: 2, 144, 756, 672, 90;

%F Formula

The row polynomials satisfy -(6*n-6-(n^3-n)*x)*P(n,x) = -(6*n-6-(n^3-13*n+12)*x-(n^3+2*n^2-n-2)*x^2)*P(n-1,x) - (12*x-(2*n^2+6*n+16)*x^2+(2*n^2+6*n+4)*x^3)*d/dx P(n-1,x) for n >= 2, with P(0,x) = 1, P(1,x) = 2.

%t Mathematica

P[0, x_] := 1;
P[1, x_] := 2;
P[n_, x_] := P[n, x] = Expand[Together[(-(6*n - 6 - (n^3 - 13*n + 12)*x - (n^3 + 2*n^2 - n - 2)*x^2)*P[n - 1, x] - (12*x - (2*n^2 + 6*n + 16)*x^2 + (2*n^2 + 6*n + 4)*x^3)*D[P[n - 1, x], x])/(-6*n + 6 + (n^3 - n)*x)]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten

%o PARI/GP

P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 2; for(n = 2, N, my(i = n + 1); v[i] = (-(6*n - 6 - (n^3 - 13*n + 12)*x - (n^3 + 2*n^2 - n - 2)*x^2)*v[i - 1] - (12*x - (2*n^2 + 6*n + 16)*x^2 + (2*n^2 + 6*n + 4)*x^3)*deriv(v[i - 1], x))/(-6*n + 6 + (n^3 - n)*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)

polytool c48629374597

Properties

Real-rooted? Every row P_n, n ≥ 0, is zero or real-rooted with all roots in (−∞, 0]
by Laguerre’s theorem on multiplier sequences
Coefficients of one sign? Every nonzero row, n ≥ 0: the coefficients of P_n have one sign
derived from Laguerre’s theorem on multiplier sequences
Hadamard kernel (Malo)? Rows P_n, n ≥ 0, are Hadamard kernels (preserve real-rootedness)
derived from Laguerre’s theorem on multiplier sequences

Proof chains ? JSON

Laguerre’s theorem on multiplier sequences [SP14; Bra15, Thm 7.1 of arXiv:1410.6601] polytool ? step ›
- from Triangle read by rows: T(n,k) is the number of circular binary words of length n having k occurrences of 01 (0 <= k <= …?
  - Liu–Wang theorem for three-term recurrences [LW07, Thm 2.1, Thm 2.3, Cor 2.4, Prop 3.3] polytool ? step › direct check

Related ?

Same fingerprint ?

References

[Bra15] Petter Brändén. Unimodality, log-concavity, real-rootedness and beyond. Handbook of enumerative combinatorics, :437–483, March 2015. doi:10.1201/b18255-10
[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
[SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.