21224560896domain: NAppears in sequencesExpansion of the sine lemniscate function sl(x).at n=16A104203a(n) = Sum_{k=0..n-1} cos(Pi*k/2)*binomial(n-1,k)*a(n-1-k)*a(k) for n > 0, a(0) = 1.at n=17A190904Expansion of Jacobi sn(x, 1/2) / cd(x, 1/2).at n=17A242240Take every fourth term of A104203.at n=4A283831