16k^2-16k-4 interleaved with 16k^2+4 for k>=0.

Terms

a(0) =-4a(1) =4a(2) =-4a(3) =20a(4) =28a(5) =68a(6) =92a(7) =148a(8) =188a(9) =260a(10) =316a(11) =404a(12) =476a(13) =580a(14) =668a(15) =788a(16) =892a(17) =1028a(18) =1148a(19) =1300a(20) =1436a(21) =1604a(22) =1756a(23) =1940a(24) =2108a(25) =2308a(26) =2492a(27) =2708a(28) =2908a(29) =3140