|
|
A133592
|
|
a(n) = 2*a(n-1)+6*a(n-2) for n>=3, a(0)=1, a(1)=2, a(2)=8.
|
|
2
|
|
|
1, 2, 8, 28, 104, 376, 1376, 5008, 18272, 66592, 242816, 885184, 3227264, 11765632, 42894848, 156383488, 570136064, 2078573056, 7577962496, 27627363328, 100722501632, 367209183232, 1338753376256, 4880761851904, 17794043961344
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
|
|
FORMULA
|
G.f.: (1-2*x^2)/(1-2*x-6*x^2).
a(n) = Sum_{k=0..n} A122950(n,k)*2^k .
a(n) = ((7+2*sqrt(7))/21)*(1+sqrt(7))^n+((7-2*sqrt(7))/21)*(1-sqrt(7))^n for n=>1. [Richard Choulet, Nov 19 2008]
|
|
MAPLE
|
option remember;
if n <=1 then
n+1;
elif n = 2 then
8;
else
2*procname(n-1)+6*procname(n-2) ;
fi ;
|
|
MATHEMATICA
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|