a(n) = (2*n+1) * (4*n-1).

Terms

a(0) =-1a(1) =9a(2) =35a(3) =77a(4) =135a(5) =209a(6) =299a(7) =405a(8) =527a(9) =665a(10) =819a(11) =989a(12) =1175a(13) =1377a(14) =1595a(15) =1829a(16) =2079a(17) =2345a(18) =2627a(19) =2925a(20) =3239a(21) =3569a(22) =3915a(23) =4277a(24) =4655a(25) =5049a(26) =5459a(27) =5885a(28) =6327a(29) =6785