40621domain: NAppears in sequencesNumber of length 3+2 0..n arrays with the sum of second differences squared multiplied by some arrangement of +-1 equal to zero.at n=21A250322E.g.f. A(x) satisfies: A(x) = exp(x) * A(x^2)^2*A(x^3)^3*A(x^4)^4* ... *A(x^k)^k* ...at n=6A307615