a(n) = n*(n+1)*(11*n+1)/6.

Terms

a(0) =0a(1) =4a(2) =23a(3) =68a(4) =150a(5) =280a(6) =469a(7) =728a(8) =1068a(9) =1500a(10) =2035a(11) =2684a(12) =3458a(13) =4368a(14) =5425a(15) =6640a(16) =8024a(17) =9588a(18) =11343a(19) =13300a(20) =15470a(21) =17864a(22) =20493a(23) =23368a(24) =26500a(25) =29900a(26) =33579a(27) =37548a(28) =41818a(29) =46400