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A155612
7^n - 3^n + 1.
8
1, 5, 41, 317, 2321, 16565, 116921, 821357, 5758241, 40333925, 282416201, 1977149597, 13840755761, 96887416085, 678218289881, 4747547161037, 33232887522881, 232630384847045, 1628413210489961, 11398894023111677
OFFSET
0,2
FORMULA
G.f.: 1/(1-7*x)-1/(1-3*x)+1/(1-x).
E.g.f.: e^(7*x)-e^(3*x)+e^x.
a(n) = 10*a(n-1)-21*a(n-2)+12 with a(0)=1, a(1)=5. - Vincenzo Librandi, Jul 21 2010
PROG
(PARI) a(n)=7^n-3^n+1 \\ Charles R Greathouse IV, Oct 07 2015
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Jan 26 2009
STATUS
approved