a(n) = (5*n^2 + n + 2)/2.

Terms

a(0) =1a(1) =4a(2) =12a(3) =25a(4) =43a(5) =66a(6) =94a(7) =127a(8) =165a(9) =208a(10) =256a(11) =309a(12) =367a(13) =430a(14) =498a(15) =571a(16) =649a(17) =732a(18) =820a(19) =913a(20) =1011a(21) =1114a(22) =1222a(23) =1335a(24) =1453a(25) =1576a(26) =1704a(27) =1837a(28) =1975a(29) =2118