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A155652
9^n-6^n+1.
17
1, 4, 46, 514, 5266, 51274, 484786, 4503034, 41367106, 377342794, 3426318226, 31018262554, 280252754146, 2528805134314, 22798428290866, 205420947110074, 1850199078944386, 16660255040221834, 149993075340330706
OFFSET
0,2
FORMULA
G.f.: 1/(1-9*x)-1/(1-6*x)+1/(1-x). E.g.f.: e^(9*x)-e^(6*x)+e^x.
a(n)=15*a(n-1)-54*a(n-2)+40 with a(0)=1, a(1)=4 - Vincenzo Librandi, Jul 21 2010
PROG
(PARI) a(n)=9^n-6^n+1^n \\ Charles R Greathouse IV, Jun 11 2015
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Jan 31 2009
STATUS
approved