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

Terms

a(0) =1a(1) =39a(2) =269a(3) =1304a(4) =3249a(5) =10491a(6) =17149a(7) =42176a(8) =66069a(9) =126711a(10) =162381a(11) =350776a(12) =373489a(13) =668811a(14) =873981a(15) =1353216a(16) =1424769a(17) =2576691a(18) =2482957a(19) =4236696a(20) =4613081a(21) =6332859a(22) =6448509a(23) =11345344a(24) =10168625a(25) =14566071a(26) =16073721a(27) =22362296a(28) =20535537a(29) =34085259