A210981 A062725 and positive terms of A051682 interleaved.

0, 1, 7, 11, 23, 30, 48, 58, 82, 95, 125, 141, 177, 196, 238, 260, 308, 333, 387, 415, 475, 506, 572, 606, 678, 715, 793, 833, 917, 960, 1050, 1096, 1192, 1241, 1343, 1395, 1503, 1558, 1672, 1730, 1850, 1911, 2037, 2101, 2233, 2300, 2438, 2508, 2652, 2725, 2875, 2951, 3107, 3186, 3348

Offset: 0

Author

Omar E. Pol, Aug 03 2012

Keywords

• nonn
• easy

Comments

Vertex number of a square spiral similar to A195160.

Links

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

Crossrefs

Members of this family are A093005, A210977, A006578, A210978, A181995, this sequence, A210982.

Cf. A051682, A062725, A195160.

Programs

Mathematica

LinearRecurrence[{1,2,-2,-1,1},{0,1,7,11,23},70] (* Harvey P. Dale, Jun 29 2023 *)

Formula

G.f.: -x*(1+6*x+2*x^2) / ( (1+x)^2*(x-1)^3 ). - R. J. Mathar, Aug 07 2012

a(n) = ( 18*n^2+14*n-5+(6*n+5)*(-1)^n )/16. - Luce ETIENNE, Oct 14 2014