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

Terms

a(0) =1a(1) =19a(2) =89a(3) =316a(4) =649a(5) =1691a(6) =2449a(7) =5104a(8) =7281a(9) =12331a(10) =14761a(11) =28124a(12) =28729a(13) =46531a(14) =57761a(15) =81856a(16) =83809a(17) =138339a(18) =130681a(19) =205084a(20) =217961a(21) =280459a(22) =280369a(23) =454256a(24) =406225a(25) =545851a(26) =590409a(27) =773884a(28) =708121a(29) =1097459