a(n) = n*(9*n + 1)/2.

Terms

a(0) =0a(1) =5a(2) =19a(3) =42a(4) =74a(5) =115a(6) =165a(7) =224a(8) =292a(9) =369a(10) =455a(11) =550a(12) =654a(13) =767a(14) =889a(15) =1020a(16) =1160a(17) =1309a(18) =1467a(19) =1634a(20) =1810a(21) =1995a(22) =2189a(23) =2392a(24) =2604a(25) =2825a(26) =3055a(27) =3294a(28) =3542a(29) =3799