a(n) = 4*n^2 - 10*n + 7.

Terms

a(0) =1a(1) =3a(2) =13a(3) =31a(4) =57a(5) =91a(6) =133a(7) =183a(8) =241a(9) =307a(10) =381a(11) =463a(12) =553a(13) =651a(14) =757a(15) =871a(16) =993a(17) =1123a(18) =1261a(19) =1407a(20) =1561a(21) =1723a(22) =1893a(23) =2071a(24) =2257a(25) =2451a(26) =2653a(27) =2863a(28) =3081a(29) =3307