a(n) = n*(7*n^2 - 3*n - 1)/3.

Terms

a(0) =0a(1) =1a(2) =14a(3) =53a(4) =132a(5) =265a(6) =466a(7) =749a(8) =1128a(9) =1617a(10) =2230a(11) =2981a(12) =3884a(13) =4953a(14) =6202a(15) =7645a(16) =9296a(17) =11169a(18) =13278a(19) =15637a(20) =18260a(21) =21161a(22) =24354a(23) =27853a(24) =31672a(25) =35825a(26) =40326a(27) =45189a(28) =50428a(29) =56057