a(n) = n*(n+1)*(5*n+1)/6.

Terms

a(0) =2a(1) =11a(2) =32a(3) =70a(4) =130a(5) =217a(6) =336a(7) =492a(8) =690a(9) =935a(10) =1232a(11) =1586a(12) =2002a(13) =2485a(14) =3040a(15) =3672a(16) =4386a(17) =5187a(18) =6080a(19) =7070a(20) =8162a(21) =9361a(22) =10672a(23) =12100a(24) =13650a(25) =15327a(26) =17136a(27) =19082a(28) =21170a(29) =23405