0,2

G.f.=(1-2z+4z^3)/[2z^2*(1-2z)sqrt(1-4z^2)]-1/(2z^2). a(2n)=(2n)!(2n^2+4n+1)/[n!(n+1)! ], a(2n+1)=2(2n+1)!/(n!)^2. a(2n+1)=2*A002457(n).

Cf. A002457.

Sequence in context: A007230 A059053 A032025 this_sequence A073710 A092831 A055257

Adjacent sequences: A088659 A088660 A088661 this_sequence A088663 A088664 A088665

nonn

Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 21 2003