a(n) = n^2*(n+1)^2*(4*n^2 - 5*n + 4)/12.

Terms

a(0) =0a(1) =1a(2) =30a(3) =300a(4) =1600a(5) =5925a(6) =17346a(7) =43120a(8) =95040a(9) =191025a(10) =356950a(11) =628716a(12) =1054560a(13) =1697605a(14) =2638650a(15) =3979200a(16) =5844736a(17) =8388225a(18) =11793870a(19) =16281100a(20) =22108800a(21) =29579781a(22) =39045490a(23) =50910960a(24) =65640000a(25) =83760625a(26) =105870726a(27) =132643980a(28) =164836000a(29) =203290725