a(n) = n*(n+1)*(22*n-19)/6.

Terms

a(0) =0a(1) =1a(2) =25a(3) =94a(4) =230a(5) =455a(6) =791a(7) =1260a(8) =1884a(9) =2685a(10) =3685a(11) =4906a(12) =6370a(13) =8099a(14) =10115a(15) =12440a(16) =15096a(17) =18105a(18) =21489a(19) =25270a(20) =29470a(21) =34111a(22) =39215a(23) =44804a(24) =50900a(25) =57525a(26) =64701a(27) =72450a(28) =80794a(29) =89755