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A019481 a(n) = 3*a(n-1) + a(n-2) - 2*a(n-3) (agrees with A019480 for n <= 19 only). 4
4, 12, 37, 115, 358, 1115, 3473, 10818, 33697, 104963, 326950, 1018419, 3172281, 9881362, 30779529, 95875387, 298642966, 930245227, 2897627873, 9025842914, 28114666161, 87574585651, 272786737286, 849705465187, 2646753961545, 8244393875250 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
REFERENCES
R. K. Guy, personal communication.
LINKS
FORMULA
From R. J. Mathar, Aug 22 2008: (Start)
O.g.f.: (4 - 3*x^2)/(1 - 3*x - x^2 + 2*x^3).
a(n) = 4*A100058(n) - 3*A100058(n-2). (End)
MATHEMATICA
LinearRecurrence[{3, 1, -2}, {4, 12, 37}, 30] (* Harvey P. Dale, Jan 17 2017 *)
PROG
(Magma) I:=[4, 12, 37]; [n le 3 select I[n] else 3*Self(n-1)+Self(n-2)-2*Self(n-3): n in [1..30]]; // Vincenzo Librandi, Jan 18 2017
CROSSREFS
Sequence in context: A033130 A196918 A099098 * A019480 A192907 A047088
KEYWORD
nonn,easy
AUTHOR
STATUS
approved

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Last modified July 13 11:10 EDT 2024. Contains 374282 sequences. (Running on oeis4.)