Number of elements in the set {(x,y): 1 <= x,y <= n, gcd(x,y)=1}.

Terms

a(0) =1a(1) =3a(2) =7a(3) =11a(4) =19a(5) =23a(6) =35a(7) =43a(8) =55a(9) =63a(10) =83a(11) =91a(12) =115a(13) =127a(14) =143a(15) =159a(16) =191a(17) =203a(18) =239a(19) =255a(20) =279a(21) =299a(22) =343a(23) =359a(24) =399a(25) =423a(26) =459a(27) =483a(28) =539a(29) =555