a(n)=60*sum(1<=i<=j<=k<=n,i^2*j/k).

Terms

a(0) =0a(1) =60a(2) =390a(3) =1450a(4) =4045a(5) =9421a(6) =19361a(7) =36281a(8) =63326a(9) =104466a(10) =164592a(11) =249612a(12) =366547a(13) =523627a(14) =730387a(15) =997763a(16) =1338188a(17) =1765688a(18) =2295978a(19) =2946558a(20) =3736809a(21) =4688089a(22) =5823829a(23) =7169629a(24) =8753354a(25) =10605230a(26) =12757940a(27) =15246720a(28) =18109455a(29) =21386775