A210978 A186029 and positive terms of A001106 interleaved.

0, 1, 5, 9, 17, 24, 36, 46, 62, 75, 95, 111, 135, 154, 182, 204, 236, 261, 297, 325, 365, 396, 440, 474, 522, 559, 611, 651, 707, 750, 810, 856, 920, 969, 1037, 1089, 1161, 1216, 1292, 1350, 1430, 1491, 1575, 1639, 1727, 1794, 1886, 1956, 2052, 2125, 2225, 2301

Offset: 0

Author

Omar E. Pol, Aug 03 2012

Keywords

• nonn
• easy

Comments

Vertex number of a square spiral similar to A118277.

Links

• Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1).

Crossrefs

Members of this family are A093005, A210977, A006578, this sequence, A181995, A210981, A210982.

Cf. A001106, A118277, A186029, A195020, A195024.

Programs

PARI

Vec(-x*(2*x^2+4*x+1)/((x-1)^3*(x+1)^2) + O(x^100)) \\ Colin Barker, Sep 15 2013

Formula

a(n) = (3*(-1+(-1)^n)+2*(5+(-1)^n)*n+14*n^2)/16. a(n) = a(n-1)+2*a(n-2)-2*a(n-3)-a(n-4)+a(n-5). G.f.: -x*(2*x^2+4*x+1) / ((x-1)^3*(x+1)^2). - Colin Barker, Sep 15 2013

Extensions

More terms from Colin Barker, Sep 15 2013