OFFSET
1,2
FORMULA
a(n) = Sum_{i=1..n} Sum_{r>=0,s>=0} binomial(r*s+i-1,i)/2^(r+s+2).
EXAMPLE
a(3) = 1 + 6 + 39 = 46.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Dec 31 2010
STATUS
approved