a(n) = n*(2*n^2 + 1)*(n^2 + 1)/6.

Terms

a(0) =1a(1) =15a(2) =95a(3) =374a(4) =1105a(5) =2701a(6) =5775a(7) =11180a(8) =20049a(9) =33835a(10) =54351a(11) =83810a(12) =124865a(13) =180649a(14) =254815a(15) =351576a(16) =475745a(17) =632775a(18) =828799a(19) =1070670a(20) =1366001a(21) =1723205a(22) =2151535a(23) =2661124a(24) =3263025a(25) =3969251a(26) =4792815a(27) =5747770a(28) =6849249a(29) =8113505