OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: Product_{i>=1} 1/(1-6*x^i).
a(n) ~ c * 6^n, where c = Product_{k>=1} 1/(1-1/6^k) = 1.2411756627857248707756... . - Vaclav Kotesovec, Mar 19 2015
G.f.: Sum_{i>=0} 6^i*x^i/Product_{j=1..i} (1 - x^j). - Ilya Gutkovskiy, Apr 12 2018
MAPLE
b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
b(n, i-1) +`if`(i>n, 0, 6*b(n-i, i))))
end:
a:= n-> b(n$2):
seq(a(n), n=0..25);
MATHEMATICA
(O[x]^20 - 5/QPochhammer[6, x])[[3]] (* Vladimir Reshetnikov, Nov 20 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Sep 08 2014
STATUS
approved