OFFSET
0,1
MAPLE
wt := proc(n) local w, m, i;
w := 0; m := n; while m > 0 do i := m mod 2; w := w+i; m := (m-i)/2; od; w; end:
f := n->add( 2^k*binomial(wt(n+k), k), k=1..20 );
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 04 2009
STATUS
approved