Number of pairs x,y such that y-x=2, (x,n)=1, (y,n)=1 and 1 <= x <= n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =1a(6) =5a(7) =4a(8) =3a(9) =3a(10) =9a(11) =2a(12) =11a(13) =5a(14) =3a(15) =8a(16) =15a(17) =3a(18) =17a(19) =6a(20) =5a(21) =9a(22) =21a(23) =4a(24) =15a(25) =11a(26) =9a(27) =10a(28) =27a(29) =3