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A081655
2*5^n-1.
22
1, 9, 49, 249, 1249, 6249, 31249, 156249, 781249, 3906249, 19531249, 97656249, 488281249, 2441406249, 12207031249, 61035156249, 305175781249, 1525878906249, 7629394531249, 38146972656249, 190734863281249
OFFSET
0,2
COMMENTS
Binomial transform of A081654. Inverse binomial transform of A081656.
FORMULA
G.f.: (1+3*x)/((1-5*x)*(1-x)).
E.g.f. 2*exp(5*x)-exp(x).
a(n) = 5*a(n-1)+4, with a(0)=1. - Vincenzo Librandi, Aug 01 2010
MATHEMATICA
CoefficientList[Series[(1 + 3 x) / ((1 - 5 x) (1 - x)), {x, 0, 40}], x] (* Vincenzo Librandi, Aug 10 2013 *)
NestList[5#+4&, 1, 30] (* Harvey P. Dale, Jul 04 2014 *)
PROG
(Magma) [2*5^n-1: n in [0..30]]; // Vincenzo Librandi, Aug 10 2013
(PARI) a(n)=2*5^n-1 \\ Charles R Greathouse IV, Sep 24 2015
CROSSREFS
Sequence in context: A060867 A192814 A228018 * A181539 A224473 A146798
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Mar 26 2003
STATUS
approved