a(n) = Sum_{i=1..n, j=1..n, gcd(i,j)=1} (n+1-i)*(n+1-j).

Terms

a(0) =1a(1) =8a(2) =31a(3) =80a(4) =179a(5) =332a(6) =585a(7) =948a(8) =1463a(9) =2136a(10) =3065a(11) =4216a(12) =5729a(13) =7568a(14) =9797a(15) =12456a(16) =15737a(17) =19520a(18) =24087a(19) =29308a(20) =35315a(21) =42120a(22) =50073a(23) =58920a(24) =69025a(25) =80264a(26) =92871a(27) =106756a(28) =122475a(29) =139528