a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} gcd(x_1, x_2, x_3, n)^4.

Terms

a(0) =1a(1) =23a(2) =107a(3) =424a(4) =749a(5) =2461a(6) =2743a(7) =7232a(8) =9369a(9) =17227a(10) =15971a(11) =45368a(12) =30757a(13) =63089a(14) =80143a(15) =119296a(16) =88433a(17) =215487a(18) =137179a(19) =317576a(20) =293501a(21) =367333a(22) =292007a(23) =773824a(24) =483625a(25) =707411a(26) =777843a(27) =1163032a(28) =731669a(29) =1843289