a(n) = n*(n-1)*(n-2)*(3*n-2)/6.

Terms

a(0) =0a(1) =0a(2) =0a(3) =7a(4) =40a(5) =130a(6) =320a(7) =665a(8) =1232a(9) =2100a(10) =3360a(11) =5115a(12) =7480a(13) =10582a(14) =14560a(15) =19565a(16) =25760a(17) =33320a(18) =42432a(19) =53295a(20) =66120a(21) =81130a(22) =98560a(23) =118657a(24) =141680a(25) =167900a(26) =197600a(27) =231075a(28) =268632a(29) =310590