A146987 → basis A013611

nonnegative coefficients

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

Recurrence

\(\left(-3 + n\right)\,P_{n}(x) = \left(36 + 144\,x + 144\,x^{2} - 12\,n - 48\,n x - 48\,n x^{2}\right)\,P_{n-2}(x) + \left(-24 - 48\,x + 8\,n + 16\,n x\right)\,P_{n-1}(x)\)

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

\(P_{1}(x) = 2 + 4\,x\)

\(P_{2}(x) = 7 + 28\,x + 16\,x^{2}\)

\(P_{3}(x) = 26 + 156\,x + 240\,x^{2} + 64\,x^{3}\)

Rows ?

n	x⁰	x¹	x²	x³	x⁴	x⁵	x⁶	x⁷	P_n(1)
0	1								1
1	2	4							6
2	7	28	16						51
3	26	156	240	64					486
4	124	992	2544	2240	256				6156
5	680	6800	24608	38848	23296	1024			95256
6	3952	47424	221568	507904	575232	261120	4096		1621296
7	23456	328384	1876992	5634560	9402880	8297472	3043328	16384	28623456

All 15 rows

Technical details

Node id: n-3f2d3a36a2f92f4a · revision 0 · JSON
Definition source: derived:basis_map_A013611
Fingerprint: f6-28c423639b74b313

Observed on the stored rows ?

Degrees: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 (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,        4;
  2:      7,       28,        16;
  3:     26,      156,       240,        64;
  4:    124,      992,      2544,      2240,        256;
  5:    680,     6800,     24608,     38848,      23296,       1024;
  6:   3952,    47424,    221568,    507904,     575232,     261120,       4096;
  7:  23456,   328384,   1876992,   5634560,    9402880,    8297472,    3043328,      16384;
  8: 140224,  2243584,  15145216,  56101888,  123458560,  161701888,  116912128,   36093952,     65536;
  9: 840320, 15125760, 117646848, 517665792, 1411909632, 2447585280, 2636390400, 1614790656, 431161344, 262144;

%F Formula

The row polynomials satisfy (n-3)*P(n,x) = -(12*n-36+(48*n-144)*x+(48*n-144)*x^2)*P(n-2,x) + (8*n-24+(16*n-48)*x)*P(n-1,x) for n >= 4, with P(0,x) = 1, P(1,x) = 2 + 4*x, P(2,x) = 7 + 28*x + 16*x^2, P(3,x) = 26 + 156*x + 240*x^2 + 64*x^3.

%t Mathematica

P[0, x_] := 1;
P[1, x_] := 2 + 4*x;
P[2, x_] := 7 + 28*x + 16*x^2;
P[3, x_] := 26 + 156*x + 240*x^2 + 64*x^3;
P[n_, x_] := P[n, x] = Expand[Together[(-(12*n - 36 + (48*n - 144)*x + (48*n - 144)*x^2)*P[n - 2, x] + (8*n - 24 + (16*n - 48)*x)*P[n - 1, x])/(n - 3)]];
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 + 4*x; v[3] = 7 + 28*x + 16*x^2; v[4] = 26 + 156*x + 240*x^2 + 64*x^3; for(n = 4, N, my(i = n + 1); v[i] = (-(12*n - 36 + (48*n - 144)*x + (48*n - 144)*x^2)*v[i - 2] + (8*n - 24 + (16*n - 48)*x)*v[i - 1])/(n - 3)); 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 Geometric basis map (elementary)
Coefficients of one sign? Every nonzero row, n ≥ 0: the coefficients of P_n have one sign
derived from Geometric basis map (elementary)
Hadamard kernel (Malo)? Rows P_n, n ≥ 0, are Hadamard kernels (preserve real-rootedness)
derived from Geometric basis map (elementary)
Interlacing of consecutive rows? Rows P_(m-1), P_m interlace (weak, unordered) for every m ≥ 3
by Geometric basis map (elementary)

Proof chains ? JSON

Geometric basis map (elementary) polytool ? step ›
- from Triangle, read by rows, T(n, k) = binomial(n, k) for n < 2 and binomial(n, k) + 3^(n-1)*binomial(n-2, k -1) otherwise.?
  - Liu–Wang theorem for three-term recurrences [LW07, Thm 2.1, Thm 2.3, Cor 2.4, Prop 3.3] polytool ? step › direct check

References

[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