a(n) = Sum_{1 <= i, j, k <= n} gcd(i,j,k).

Terms

a(0) =1a(1) =9a(2) =30a(3) =76a(4) =141a(5) =267a(6) =400a(7) =624a(8) =885a(9) =1249a(10) =1590a(11) =2208a(12) =2689a(13) =3411a(14) =4248a(15) =5248a(16) =6081a(17) =7485a(18) =8530a(19) =10248a(20) =11889a(21) =13687a(22) =15228a(23) =17988a(24) =20053a(25) =22569a(26) =25242a(27) =28588a(28) =31053a(29) =35463