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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).
a(n) = A176805(n) - 1.
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
Sequence in context: A128443 A245470 A135854 * A083011 A299267 A254008
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Mar 02 2013
STATUS
approved

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Last modified March 29 05:48 EDT 2024. Contains 371265 sequences. (Running on oeis4.)