a(n) = n! * |Stirling1(2*n, n)|.A376873a(n) = n! * |Stirling1(2*n, n)|.Terms a(0) =1a(1) =1a(2) =22a(3) =1350a(4) =162456a(5) =32319000a(6) =9604465200External referencesoeis: A376873