OFFSET
0,2
COMMENTS
a(n) is the number of generalized compositions of n when there are 3*2^(i-1) different types of i, (i=1,2,...). - Milan Janjic, Sep 24 2010
INVERTi transform of A180034: (1, 4, 22, 124, 700, ...). - Gary W. Adamson, Aug 10 2016
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets.
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 883.
Index entries for linear recurrences with constant coefficients, signature (5).
FORMULA
Binomial transform of A122117. - Philippe Deléham, Oct 19 2006
a(0) = 1, a(n) = 3*5^(n-1) for n >= 1. - Philippe Deléham, Oct 19 2006
E.g.f.: (2 + 3*exp(5*x))/5. - Ilya Gutkovskiy, Aug 11 2016
MATHEMATICA
CoefficientList[Series[(1-2x)/(1-5x), {x, 0, 30}], x] (* or *) Join[{1}, NestList[5#&, 3, 29]] (* Harvey P. Dale, Apr 25 2011 *)
PROG
(Magma) [ n eq 0 select 1 else 3*5^(n-1): n in [0..20] ]; // Klaus Brockhaus, Apr 04 2010
(PARI) my(x='x+O('x^50)); Vec((1-2*x)/(1-5*x)) \\ G. C. Greubel, Sep 15 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Wrong formula deleted by Klaus Brockhaus, Apr 04 2010
STATUS
approved
