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A155640
a(n) = 7^n - 5^n + 1^n.
21
1, 3, 25, 219, 1777, 13683, 102025, 745419, 5374177, 38400483, 272709625, 1928498619, 13597146577, 95668307283, 672119557225, 4717043931819, 33080342678977, 231867574534083, 1624598900644825, 11379821699045019, 79696898865971377, 558069026925080883
OFFSET
0,2
FORMULA
G.f.: 1/(1-7*x)-1/(1-5*x)+1/(1-x).
E.g.f.: e^(7*x)-e^(5*x)+e^x.
a(n) = 12*a(n-1)-35*a(n-2)+24 with a(0)=1, a(1)=3. - Vincenzo Librandi, Jul 21 2010
MATHEMATICA
Table[7^n - 5^n + 1, {n, 0, 25}] (* Paolo Xausa, Jul 26 2024 *)
PROG
(PARI) a(n)=7^n-5^n+1 \\ Charles R Greathouse IV, Sep 24 2015
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Jan 30 2009
STATUS
approved