a(n) = (16/3)*(n+1)*n*(n-1) + 8*n^2 + 1.

Terms

a(0) =9a(1) =65a(2) =201a(3) =449a(4) =841a(5) =1409a(6) =2185a(7) =3201a(8) =4489a(9) =6081a(10) =8009a(11) =10305a(12) =13001a(13) =16129a(14) =19721a(15) =23809a(16) =28425a(17) =33601a(18) =39369a(19) =45761a(20) =52809a(21) =60545a(22) =69001a(23) =78209a(24) =88201a(25) =99009a(26) =110665a(27) =123201a(28) =136649a(29) =151041