a(n) = n*(19*n-15)/2.

Terms

a(0) =0a(1) =2a(2) =23a(3) =63a(4) =122a(5) =200a(6) =297a(7) =413a(8) =548a(9) =702a(10) =875a(11) =1067a(12) =1278a(13) =1508a(14) =1757a(15) =2025a(16) =2312a(17) =2618a(18) =2943a(19) =3287a(20) =3650a(21) =4032a(22) =4433a(23) =4853a(24) =5292a(25) =5750a(26) =6227a(27) =6723a(28) =7238a(29) =7772