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A051407
a(n) = 3^n*(3^(n+1)+1)/2.
1
2, 15, 126, 1107, 9882, 88695, 797526, 7175547, 64573362, 581140575, 5230206126, 47071677987, 423644570442, 3812799539655, 34315191073926, 308836705316427, 2779530304801122, 25015772614069935, 225141953139208926, 2026277577090618867, 18236498190328785402
OFFSET
0,1
FORMULA
From Colin Barker, Feb 10 2016: (Start)
a(n) = 12*a(n-1) - 27*a(n-2) for n>1.
G.f.: (2-9*x) / ((1-3*x)*(1-9*x)). (End)
PROG
(PARI) Vec((2-9*x)/((1-3*x)*(1-9*x)) + O(x^100)) \\ Colin Barker, Feb 10 2016
CROSSREFS
Sequence in context: A341726 A055866 A364978 * A371580 A242091 A132182
KEYWORD
nonn,easy
AUTHOR
STATUS
approved