a(n) = A000043(n) * A000668(n).A131960a(n) = A000043(n) * A000668(n).Terms a(0) =6a(1) =21a(2) =155a(3) =889a(4) =106483a(5) =2228207a(6) =9961453a(7) =66571993057External referencesoeis: A131960