a(n) = n^4 - n.

Terms

a(0) =0a(1) =0a(2) =14a(3) =78a(4) =252a(5) =620a(6) =1290a(7) =2394a(8) =4088a(9) =6552a(10) =9990a(11) =14630a(12) =20724a(13) =28548a(14) =38402a(15) =50610a(16) =65520a(17) =83504a(18) =104958a(19) =130302a(20) =159980a(21) =194460a(22) =234234a(23) =279818a(24) =331752a(25) =390600a(26) =456950a(27) =531414a(28) =614628a(29) =707252