a(n) = n^4 - n - 1.

Terms

a(0) =-1a(1) =13a(2) =77a(3) =251a(4) =619a(5) =1289a(6) =2393a(7) =4087a(8) =6551a(9) =9989a(10) =14629a(11) =20723a(12) =28547a(13) =38401a(14) =50609a(15) =65519a(16) =83503a(17) =104957a(18) =130301a(19) =159979a(20) =194459a(21) =234233a(22) =279817a(23) =331751a(24) =390599a(25) =456949a(26) =531413a(27) =614627a(28) =707251a(29) =809969