a(n) = (6*n+1)*(6*n+7).

Terms

a(0) =7a(1) =91a(2) =247a(3) =475a(4) =775a(5) =1147a(6) =1591a(7) =2107a(8) =2695a(9) =3355a(10) =4087a(11) =4891a(12) =5767a(13) =6715a(14) =7735a(15) =8827a(16) =9991a(17) =11227a(18) =12535a(19) =13915a(20) =15367a(21) =16891a(22) =18487a(23) =20155a(24) =21895a(25) =23707a(26) =25591a(27) =27547a(28) =29575a(29) =31675