a(n) = n*(n+1)*(11*n +10)/6.

Terms

a(0) =0a(1) =7a(2) =32a(3) =86a(4) =180a(5) =325a(6) =532a(7) =812a(8) =1176a(9) =1635a(10) =2200a(11) =2882a(12) =3692a(13) =4641a(14) =5740a(15) =7000a(16) =8432a(17) =10047a(18) =11856a(19) =13870a(20) =16100a(21) =18557a(22) =21252a(23) =24196a(24) =27400a(25) =30875a(26) =34632a(27) =38682a(28) =43036a(29) =47705