a(n) = n^2 - floor((n+1)/2)^2.

Terms

a(0) =0a(1) =0a(2) =3a(3) =5a(4) =12a(5) =16a(6) =27a(7) =33a(8) =48a(9) =56a(10) =75a(11) =85a(12) =108a(13) =120a(14) =147a(15) =161a(16) =192a(17) =208a(18) =243a(19) =261a(20) =300a(21) =320a(22) =363a(23) =385a(24) =432a(25) =456a(26) =507a(27) =533a(28) =588a(29) =616