a(n) = ceiling((n+1)^4/2).

Terms

a(0) =1a(1) =8a(2) =41a(3) =128a(4) =313a(5) =648a(6) =1201a(7) =2048a(8) =3281a(9) =5000a(10) =7321a(11) =10368a(12) =14281a(13) =19208a(14) =25313a(15) =32768a(16) =41761a(17) =52488a(18) =65161a(19) =80000a(20) =97241a(21) =117128a(22) =139921a(23) =165888a(24) =195313a(25) =228488a(26) =265721a(27) =307328a(28) =353641a(29) =405000