C(2*n,n)*stirling2(2*n,n).A124103C(2*n,n)*stirling2(2*n,n).Terms a(0) =1a(1) =2a(2) =42a(3) =1800a(4) =119070a(5) =10716300a(6) =1223054448a(7) =169298088960External referencesoeis: A124103