20k^2-20k-5 interleaved with 20k^2+5 for k=>0.

Terms

a(0) =-5a(1) =5a(2) =-5a(3) =25a(4) =35a(5) =85a(6) =115a(7) =185a(8) =235a(9) =325a(10) =395a(11) =505a(12) =595a(13) =725a(14) =835a(15) =985a(16) =1115a(17) =1285a(18) =1435a(19) =1625a(20) =1795a(21) =2005a(22) =2195a(23) =2425a(24) =2635a(25) =2885a(26) =3115a(27) =3385a(28) =3635a(29) =3925