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A154118
Expansion of (1 - x + 5x^2)/((1-x)*(1-2x)).
4
1, 2, 9, 23, 51, 107, 219, 443, 891, 1787, 3579, 7163, 14331, 28667, 57339, 114683, 229371, 458747, 917499, 1835003, 3670011, 7340027, 14680059, 29360123, 58720251, 117440507, 234881019, 469762043, 939524091, 1879048187, 3758096379, 7516192763, 15032385531
OFFSET
0,2
COMMENTS
Binomial transform of 1,1,6,1,6,1,6,1,6,1,6,1,6,1,6,...
FORMULA
a(n) = 7*2^(n-1) - 5, n>=1, with a(0)=1.
a(n) = 2*a(n-1) + 5, n>1, with a(0)=1, a(1)=2.
a(n) = 3*a(n-1) - 2*a(n-2), n>2, with a(0)=1, a(1)=2, a(2)=9.
E.g.f.: (1/2)*(5 - 10*exp(x) + 7*exp(2*x)). - G. C. Greubel, Sep 02 2016
MATHEMATICA
Join[{1}, Table[7*2^(n-1)-5, {n, 15}]] (* Vladimir Joseph Stephan Orlovsky, Mar 14 2011*)
Join[{1, 2, 9}, LinearRecurrence[{3, -2}, {23, 51}, 20]] (* G. C. Greubel, Sep 02 2016 *)
PROG
(PARI) a(n)=if(n, 7<<(n-1)-5, 1) \\ Charles R Greathouse IV, Jan 17 2012
CROSSREFS
Sequence in context: A023654 A062445 A009304 * A296284 A376750 A115185
KEYWORD
nonn,easy,less
AUTHOR
Philippe Deléham, Jan 05 2009
STATUS
approved