a(n) = binomial(n^2,n+1)/n.A177456a(n) = binomial(n^2,n+1)/n.Terms a(0) =2a(1) =42a(2) =1092a(3) =35420a(4) =1391280a(5) =64425438a(6) =3442573064a(7) =208710267480External referencesoeis: A177456