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

Terms

a(0) =0a(1) =4a(2) =35a(3) =140a(4) =390a(5) =880a(6) =1729a(7) =3080a(8) =5100a(9) =7980a(10) =11935a(11) =17204a(12) =24050a(13) =32760a(14) =43645a(15) =57040a(16) =73304a(17) =92820a(18) =115995a(19) =143260a(20) =175070a(21) =211904a(22) =254265a(23) =302680a(24) =357700a(25) =419900a(26) =489879a(27) =568260a(28) =655690a(29) =752840