3056887680domain: NAppears in sequencesa(n) = 2*Catalan(n) - Catalan(n-1).at n=18A000782a(n) = (7*n+2)*C(n)/(n+2), where C(n) is the n-th Catalan number.at n=17A061557a(n) = (2*n + 4)!*(n^2 + 11*n + 2)/(2*(n-1)!*(n+6)!).at n=13A294445