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A155630
a(n) = 9^n-4^n+1^n.
20
1, 6, 66, 666, 6306, 58026, 527346, 4766586, 42981186, 387158346, 3485735826, 31376865306, 282412759266, 2541798719466, 22876524019506, 205890058352826, 1853015893884546, 16677164519797386, 150094566577522386
OFFSET
0,2
FORMULA
G.f.: 1/(1-9*x)-1/(1-4*x)+1/(1-x). E.g.f.: e^(9*x)-e^(4*x)+e^x.
a(n) = 13*a(n-1)-36*a(n-2)+24 with a(0)=1, a(1)=6. - Vincenzo Librandi, Jul 21 2010
MATHEMATICA
Table[9^n-4^n+1, {n, 0, 20}] (* or *) LinearRecurrence[{14, -49, 36}, {1, 6, 66}, 20] (* Harvey P. Dale, Aug 08 2019 *)
PROG
(PARI) a(n)=9^n-4^n+1 \\ Charles R Greathouse IV, Sep 24 2015
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Jan 30 2009
STATUS
approved