a(n) = (3*n+1)! * Sum_{k=0..n} 1 / (3*k+1)!.A337725a(n) = (3*n+1)! * Sum_{k=0..n} 1 / (3*k+1)!.Terms a(0) =1a(1) =25a(2) =5251a(3) =3780721a(4) =6487717237External referencesoeis: A337725