a(n) = Sum_{ i=2..n-1, j=1..i-1, gcd(i,j)=1 } (n-i)*(n-j).

Terms

a(0) =0a(1) =0a(2) =2a(3) =11a(4) =32a(5) =77a(6) =148a(7) =268a(8) =442a(9) =691a(10) =1018a(11) =1472a(12) =2036a(13) =2780a(14) =3686a(15) =4786a(16) =6100a(17) =7724a(18) =9598a(19) =11863a(20) =14454a(21) =17437a(22) =20818a(23) =24772a(24) =29172a(25) =34200a(26) =39794a(27) =46071a(28) =52986a(29) =60817