A176818 a(n) = (3^(2*n+1) + 2^(n+2))/7.

1, 5, 37, 317, 2821, 25325, 227797, 2049917, 18448741, 166037645, 1494336757, 13449026717, 121041232261, 1089371073965, 9804339632917, 88239056630717, 794151509545381, 7147363585646285, 64326272270292277, 578936450431581917

Offset

0,2

Comments

3^(2*n+1) + 2^(n+2) = 3*(3^2)^n + 4*2^n == 3*2^n + 4*2^n = 7*2^n == 0 (mod 7).

Links

Table of n, a(n) for n=0..19.

Index entries for linear recurrences with constant coefficients, signature (11,-18).

Formula

G.f.: ( 1-6*x ) / ( (9*x-1)*(2*x-1) ). - R. J. Mathar, Feb 18 2016

Example

a(2) = (3^5 + 2^4)/7 = 259/7 = 37.

Maple

a:= n-> (3^(2*n+1) + 2^(n+2))/7:
seq (a(n), n=0..30);

Crossrefs

Sequence in context: A084212 A358883 A323219 * A359643 A068785 A378892

Adjacent sequences: A176815 A176816 A176817 * A176819 A176820 A176821

Keyword

nonn,easy

Author

Michel Lagneau, Apr 26 2010

Status

approved