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A155605
7^n+3^n-1.
10
1, 9, 57, 369, 2481, 17049, 118377, 825729, 5771361, 40373289, 282534297, 1977503889, 13841818641, 96890604729, 678227855817, 4747575858849, 33232973616321, 232630643127369, 1628413985330937, 11398896347634609
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)=9 - Vincenzo Librandi, Jul 21 2010
a(0)=1, a(1)=9, a(2)=57, a(n)=11*a(n-1)-31*a(n-2)+21*a(n-3). - Harvey P. Dale, Nov 09 2012
MATHEMATICA
Table[7^n+3^n-1, {n, 0, 20}] (* or *) LinearRecurrence[{11, -31, 21}, {1, 9, 57}, 20] (* Harvey P. Dale, Nov 09 2012 *)
PROG
(PARI) a(n)=7^n+3^n-1 \\ Charles R Greathouse IV, Jun 11 2015
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Jan 25 2009
STATUS
approved