a(n) = Sum_{1 <= i < j <= n} (i*j)^4.

Terms

a(0) =0a(1) =0a(2) =16a(3) =1393a(4) =26481a(5) =247731a(6) =1516515a(7) =6978790a(8) =26131686a(9) =83684778a(10) =237014778a(11) =607915231a(12) =1436816095a(13) =3170754405a(14) =6600189141a(15) =13064343516a(16) =24750198748a(17) =45116627556a(18) =79482515700a(19) =135826148445a(20) =225852708445a(21) =366397514791a(22) =581244702423a(23) =903454469346