a(n) = 4*n^2 + floor(n/2).

Terms

a(0) =0a(1) =4a(2) =17a(3) =37a(4) =66a(5) =102a(6) =147a(7) =199a(8) =260a(9) =328a(10) =405a(11) =489a(12) =582a(13) =682a(14) =791a(15) =907a(16) =1032a(17) =1164a(18) =1305a(19) =1453a(20) =1610a(21) =1774a(22) =1947a(23) =2127a(24) =2316a(25) =2512a(26) =2717a(27) =2929a(28) =3150a(29) =3378