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A155629
a(n) = 8^n - 4^n + 1.
22
1, 5, 49, 449, 3841, 31745, 258049, 2080769, 16711681, 133955585, 1072693249, 8585740289, 68702699521, 549688705025, 4397778075649, 35183298347009, 281470681743361, 2251782633816065, 18014329790005249, 144114913197948929, 1152920405095219201, 9223367638808264705
OFFSET
0,2
FORMULA
G.f.: 1/(1-8*x)-1/(1-4*x)+1/(1-x).
E.g.f.: exp(8*x)-exp(4*x)+exp(x).
a(n) = 12*a(n-1)-32*a(n-2)+21 with a(0) = 1, a(1) = 5. - Vincenzo Librandi, Jul 21 2010
MATHEMATICA
Table[8^n - 4^n + 1, {n, 0, 25}] (* Paolo Xausa, Jul 30 2024 *)
PROG
(PARI) a(n)=8^n-4^n+1 \\ Charles R Greathouse IV, Sep 24 2015
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Jan 30 2009
STATUS
approved