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A199113
a(n) = (11*3^n+1)/2.
4
6, 17, 50, 149, 446, 1337, 4010, 12029, 36086, 108257, 324770, 974309, 2922926, 8768777, 26306330, 78918989, 236756966, 710270897, 2130812690, 6392438069, 19177314206, 57531942617, 172595827850, 517787483549, 1553362450646, 4660087351937
OFFSET
0,1
FORMULA
a(n) = 3*a(n-1)-1.
a(n) = 4*a(n-1)-3*a(n-2).
G.f.: (6-7*x)/((1-x)*(1-3*x)). - Bruno Berselli, Nov 04 2011
MATHEMATICA
LinearRecurrence[{4, -3}, {6, 17}, 30] (* or *) (11 3^Range[0, 30]+1)/2 (* Harvey P. Dale, Mar 25 2012 *)
PROG
(Magma) [(11*3^n+1)/2: n in [0..30]];
CROSSREFS
Sequence in context: A128525 A083334 A373040 * A297297 A241352 A239796
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 04 2011
STATUS
approved