a(n) = (n+3)^2 - 6.

Terms

a(0) =3a(1) =10a(2) =19a(3) =30a(4) =43a(5) =58a(6) =75a(7) =94a(8) =115a(9) =138a(10) =163a(11) =190a(12) =219a(13) =250a(14) =283a(15) =318a(16) =355a(17) =394a(18) =435a(19) =478a(20) =523a(21) =570a(22) =619a(23) =670a(24) =723a(25) =778a(26) =835a(27) =894a(28) =955a(29) =1018