A085963 Denominators of Farey fractions with prime numerators and denominators.

3, 5, 5, 3, 7, 5, 7, 5, 3, 7, 11, 11, 7, 5, 7, 11, 5, 11, 3, 7, 13, 11, 13, 11, 7, 13, 5, 7, 11, 13, 5, 11, 3, 7, 13, 17, 13, 17, 11, 13, 11, 7, 17, 13, 5, 17, 7, 11, 13, 5, 11, 17, 3, 7, 17, 13, 19, 17, 13, 19, 17, 11, 13, 19, 11, 7, 17, 19, 13, 5, 17, 7, 11, 13, 19, 5, 11, 17, 3, 19, 7

Offset: 3

Author

Cino Hilliard, Aug 17 2003

Keywords

• easy
• nonn

Crossrefs

Cf. A085692.

Programs

PARI

\ Farey sequence of order n fareyct(n) = { forprime(x=2,n, y = farey(x); \ print1(y","); ) } farey(n) = { c=0; m=n*(n-2)+2; a=vector(m); forprime(x=1,n, forprime(y=x,n, v = x/y; if(v<1, c++; a[c]=v; ) ) ); a = vecsort(a); c=0; for(x=2,m, if(a[x]<>a[x-1] & a[x]<>0, print1(numerator(a[x])","); c++; ) ); return(c) }