a(n) = Sum_{x_1|n, x_2|n, ... , x_n|n} gcd(x_1,x_2, ... ,x_n).

Terms

a(0) =1a(1) =5a(2) =10a(3) =99a(4) =36a(5) =4290a(6) =134a(7) =72613a(8) =20713a(9) =1053700a(10) =2058a(11) =2194638822a(12) =8204a(13) =268550150a(14) =1073938440a(15) =156969213515a(16) =131088a(18) =524306a(22) =8388630a(24) =847422827191