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A074621
a(n) = 6^n + 9^n.
1
2, 15, 117, 945, 7857, 66825, 578097, 5062905, 44726337, 397498185, 3547250577, 31743856665, 284606318817, 2554926522345, 22955156619057, 206361317079225, 1855841298759297, 16694108359111305, 150196195253667537
OFFSET
0,1
FORMULA
From Mohammad K. Azarian, Jan 11 2009: (Start)
G.f.: 1/(1-6*x) + 1/(1-9*x).
E.g.f.: e^(6*x) + e^(9*x). (End)
a(n) = 15*a(n-1) - 54*a(n-2) with a(0)=2, a(1)=15. - Vincenzo Librandi, Jul 21 2010
MATHEMATICA
Table[6^n + 9^n, {n, 0, 20}]
KEYWORD
easy,nonn
AUTHOR
Robert G. Wilson v, Aug 26 2002
STATUS
approved