|
|
A176961
|
|
a(n) = (3*2^(n+1) - 8 - (-2)^n)/6.
|
|
1
|
|
|
1, 2, 8, 12, 36, 52, 148, 212, 596, 852, 2388, 3412, 9556, 13652, 38228, 54612, 152916, 218452, 611668, 873812, 2446676, 3495252, 9786708, 13981012, 39146836, 55924052, 156587348, 223696212, 626349396, 894784852
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
a(n) = a(n-1) + 4*a(n-2) - 4*a(n-3).
G.f.: x*(1 + x + 2*x^2) / ((x-1)*(2*x+1)*(2*x-1)). - R. J. Mathar, Apr 30 2010
|
|
MATHEMATICA
|
a[1] := 1;
a[n_] := a[n] = a[n - 1]/2 + Sqrt[(5 + 4*(-1)^(n - 1))]/2:
Table[2^(n - 1)*a[n], {n, 1, 30}]
|
|
PROG
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|