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A155604
a(n) = 6^n + 3^n - 1.
11
1, 8, 44, 242, 1376, 8018, 47384, 282122, 1686176, 10097378, 60525224, 362974202, 2177313776, 13062288338, 78368947064, 470199333482, 2821152954176, 16926788584898, 101560344088904, 609360902271962, 3656161926847376
OFFSET
0,2
FORMULA
G.f.: 1/(1-6*x)+1/(1-3*x)-1/(1-x).
E.g.f.: exp(6*x)+exp(3*x)-exp(x).
a(n) = 9*a(n-1)-18*a(n-2)-10 with a(0) = 1, a(1) = 8. - Vincenzo Librandi, Jul 21 2010
MATHEMATICA
Table[6^n + 3^n - 1, {n, 0, 25}] (* Paolo Xausa, Aug 21 2024 *)
PROG
(PARI) a(n)=6^n+3^n-1 \\ Charles R Greathouse IV, Jun 11 2015
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Jan 25 2009
STATUS
approved