a(n) = 36n^2 - 1.

Terms

a(0) =35a(1) =143a(2) =323a(3) =575a(4) =899a(5) =1295a(6) =1763a(7) =2303a(8) =2915a(9) =3599a(10) =4355a(11) =5183a(12) =6083a(13) =7055a(14) =8099a(15) =9215a(16) =10403a(17) =11663a(18) =12995a(19) =14399a(20) =15875a(21) =17423a(22) =19043a(23) =20735a(24) =22499a(25) =24335a(26) =26243a(27) =28223a(28) =30275a(29) =32399