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

Terms

a(0) =1a(1) =24a(2) =105a(3) =280a(4) =585a(5) =1056a(6) =1729a(7) =2640a(8) =3825a(9) =5320a(10) =7161a(11) =9384a(12) =12025a(13) =15120a(14) =18705a(15) =22816a(16) =27489a(17) =32760a(18) =38665a(19) =45240a(20) =52521a(21) =60544a(22) =69345a(23) =78960a(24) =89425a(25) =100776a(26) =113049a(27) =126280a(28) =140505a(29) =155760