a(n) = n*(9*n + 25)/2 + 6.

Terms

a(0) =6a(1) =23a(2) =49a(3) =84a(4) =128a(5) =181a(6) =243a(7) =314a(8) =394a(9) =483a(10) =581a(11) =688a(12) =804a(13) =929a(14) =1063a(15) =1206a(16) =1358a(17) =1519a(18) =1689a(19) =1868a(20) =2056a(21) =2253a(22) =2459a(23) =2674a(24) =2898a(25) =3131a(26) =3373a(27) =3624a(28) =3884a(29) =4153