A170935 b(n)*b(n+1), where b() = A000930().

1, 1, 2, 6, 12, 24, 54, 117, 247, 532, 1148, 2460, 5280, 11352, 24381, 52353, 112462, 241570, 518840, 1114416, 2393694, 5141385, 11043135, 23719608, 50947336, 109429624, 235043840, 504850560, 1084367865, 2329112625, 5002699050, 10745292366, 23079802756, 49573086472

Offset: 0

Author

N. J. A. Sloane, Feb 11 2010

Keywords

• nonn
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (1,1,3,1,-1,-1).

Programs

Mathematica

CoefficientList[Series[1/((x^3 - x^2 - 1)*(x^3 + 2*x^2 + x - 1)), {x, 0, 50}], x] (* G. C. Greubel, Apr 26 2017 *)
LinearRecurrence[{1,1,3,1,-1,-1},{1,1,2,6,12,24},40] (* Harvey P. Dale, Aug 27 2019 *)

PARI

x='x+O('x^50); Vec(1/((x^3-x^2-1)*(x^3+2*x^2+x-1))) \\ G. C. Greubel, Apr 26 2017

Formula

G.f.: 1 / ((x^3-x^2-1)*(x^3+2*x^2+x-1)). - Colin Barker, Jul 25 2013