a(n) = Sum_{k=0..n} (n!/k!)^3.A217284a(n) = Sum_{k=0..n} (n!/k!)^3.Terms a(0) =1a(1) =2a(2) =17a(3) =460a(4) =29441a(5) =3680126a(6) =794907217a(7) =272653175432External referencesoeis: A217284