|
|
A221905
|
|
a(n) = 3^n + 3*n.
|
|
2
|
|
|
1, 6, 15, 36, 93, 258, 747, 2208, 6585, 19710, 59079, 177180, 531477, 1594362, 4783011, 14348952, 43046769, 129140214, 387420543, 1162261524, 3486784461, 10460353266, 31381059675, 94143178896, 282429536553
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
|
|
FORMULA
|
G.f.: (1 + x - 8*x^2)/((1-x)^2*(1-3*x)).
a(n) = 5*a(n-1) - 7*a(n-2) + 3*a(n-3).
|
|
MATHEMATICA
|
Table[(3^n + 3 n), {n, 0, 30}] (* or *) CoefficientList[Series[(1 + x - 8 x^2)/((1 - x)^2 (1 -3 x)), {x, 0, 30}], x]
|
|
PROG
|
(Magma) [3^n+3*n: n in [0..30]]; /* or */ I:=[1, 6, 15]; [n le 3 select I[n] else 5*Self(n-1)-7*Self(n-2)+3*Self(n-3): n in [1..30]];
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|