a(n) = (4*n+1)*(4*n+3).

Terms

a(0) =3a(1) =35a(2) =99a(3) =195a(4) =323a(5) =483a(6) =675a(7) =899a(8) =1155a(9) =1443a(10) =1763a(11) =2115a(12) =2499a(13) =2915a(14) =3363a(15) =3843a(16) =4355a(17) =4899a(18) =5475a(19) =6083a(20) =6723a(21) =7395a(22) =8099a(23) =8835a(24) =9603a(25) =10403a(26) =11235a(27) =12099a(28) =12995a(29) =13923