OFFSET
0,3
EXAMPLE
G.f. A(x) = 1 + x + 3*x^2 + 11*x^3 + 47*x^4 + 221*x^5 + 1115*x^6 + 5947*x^7 + 33231*x^8 + ...
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 20 2018
STATUS
approved