6782469540domain: NAppears in sequencesExpansion of (1+x^4*C^2)*C^2, where C = (1-(1-4*x)^(1/2))/(2*x) is g.f. for Catalan numbers, A000108.at n=19A071747a(n) is the total number of vertices of degree 1 in Catalan word grid graphs with n parts.at n=17A390111