a(n) = n^3 + (-1)^(n+1).

Terms

a(0) =-1a(1) =2a(2) =7a(3) =28a(4) =63a(5) =126a(6) =215a(7) =344a(8) =511a(9) =730a(10) =999a(11) =1332a(12) =1727a(13) =2198a(14) =2743a(15) =3376a(16) =4095a(17) =4914a(18) =5831a(19) =6860a(20) =7999a(21) =9262a(22) =10647a(23) =12168a(24) =13823a(25) =15626a(26) =17575a(27) =19684a(28) =21951a(29) =24390