A094741 Number of primes of the form k+1 where k is coprime to n, k < n.

0, 1, 2, 1, 3, 1, 4, 1, 3, 1, 5, 1, 6, 1, 3, 1, 7, 1, 8, 1, 5, 1, 9, 1, 8, 1, 6, 1, 10, 1, 11, 1, 6, 1, 8, 1, 12, 1, 7, 1, 13, 1, 14, 1, 6, 1, 15, 1, 13, 1, 9, 1, 16, 1, 12, 1, 10, 1, 17, 1, 18, 1, 10, 1, 13, 1, 19, 1, 10, 1, 20, 1, 21, 1, 9, 1, 16, 1, 22, 1, 12, 1, 23, 1, 18, 1, 12

Offset

1,3

Comments

If n is a prime, a(n) = pi(n). If n is even, a(n) = 1.

Links

Table of n, a(n) for n=1..87.

Mathematica

A094741[ n_ ] := Length[ Select[ Select[ Range[ n - 1 ], GCD[ #, n ] == 1 & ] + 1, PrimeQ ] ]; Table[ A094741[ i ], {i, 1, 100} ]  (* Keith Schneider, Jul 03 2007 *)

Crossrefs

Sequence in context: A218533 A328578 A351613 * A360653 A285577 A362470

Adjacent sequences: A094738 A094739 A094740 * A094742 A094743 A094744

Keyword

nonn

Author

Amarnath Murthy, May 24 2004

Extensions

More terms from Keith Schneider, Jul 03 2007

Status

approved