A188129 a(n) = (2^n+3)^2-8.

8, 17, 41, 113, 353, 1217, 4481, 17153, 67073, 265217, 1054721, 4206593, 16801793, 67158017, 268533761, 1073938433, 4295360513, 17180655617, 68721049601, 274881052673, 1099517919233, 4398059094017, 17592211210241, 70368794509313, 281475077373953, 1125900108169217, 4503600030023681, 18014399314788353, 72057595648540673

Offset: 0

Author

N. J. A. Sloane, Apr 14 2011

Keywords

• nonn
• easy

Links

• Daniel Shanks, Gauss's ternary form reduction and the 2-Sylow subgroup, Math. Comp. 25 (1971), 837-853.
• Index entries for linear recurrences with constant coefficients, signature (7,-14,8).

Crossrefs

For primes see A188661 and A188936.

Programs

Mathematica

(2^Range[0,30]+3)^2-8 (* or *) LinearRecurrence[{7,-14,8},{8,17,41},30] (* Harvey P. Dale, Nov 23 2012 *)

Formula

a(n) = 7*a(n-1)-14*a(n-2)+8*a(n-3). G.f.: -(34*x^2-39*x+8)/((x-1)*(2*x-1)*(4*x-1)). [Colin Barker, Nov 11 2012]