|
|
A176818
|
|
a(n) = (3^(2*n+1) + 2^(n+2))/7.
|
|
0
|
|
|
1, 5, 37, 317, 2821, 25325, 227797, 2049917, 18448741, 166037645, 1494336757, 13449026717, 121041232261, 1089371073965, 9804339632917, 88239056630717, 794151509545381, 7147363585646285, 64326272270292277, 578936450431581917
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
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
|
|
|
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
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|