a(n) = n^6 + n^5 + n^4 + n^3 + n^2 + n.

Terms

a(0) =0a(1) =6a(2) =126a(3) =1092a(4) =5460a(5) =19530a(6) =55986a(7) =137256a(8) =299592a(9) =597870a(10) =1111110a(11) =1948716a(12) =3257436a(13) =5229042a(14) =8108730a(15) =12204240a(16) =17895696a(17) =25646166a(18) =36012942a(19) =49659540a(20) =67368420a(21) =90054426a(22) =118778946a(23) =154764792a(24) =199411800a(25) =254313150a(26) =321272406a(27) =402321276a(28) =499738092