a(n) = (27*n^2 + 9*n + 2)/2.

Terms

a(0) =1a(1) =19a(2) =64a(3) =136a(4) =235a(5) =361a(6) =514a(7) =694a(8) =901a(9) =1135a(10) =1396a(11) =1684a(12) =1999a(13) =2341a(14) =2710a(15) =3106a(16) =3529a(17) =3979a(18) =4456a(19) =4960a(20) =5491a(21) =6049a(22) =6634a(23) =7246a(24) =7885a(25) =8551a(26) =9244a(27) =9964a(28) =10711a(29) =11485