a(n) = Sum_{1 <= x_1, x_2, x_3, x_4 <= n} gcd(x_1, x_2, x_3, x_4, n)^5.

Terms

a(0) =1a(1) =47a(2) =323a(3) =1744a(4) =3749a(5) =15181a(6) =19207a(7) =59648a(8) =84969a(9) =176203a(10) =175691a(11) =563312a(12) =399853a(13) =902729a(14) =1210927a(15) =1970176a(16) =1503377a(17) =3993543a(18) =2606419a(19) =6538256a(20) =6203861a(21) =8257477a(22) =6716183a(23) =19266304a(24) =12105625a(25) =18793091a(26) =21172347a(27) =33497008a(28) =21218429a(29) =56913569