a(n) = Sum_{k=0..n} Stirling2(n+3*k,k).A392749a(n) = Sum_{k=0..n} Stirling2(n+3*k,k).Terms a(0) =1a(1) =1a(2) =128a(3) =86782a(4) =172061038a(5) =749901217784External referencesoeis: A392749