login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A094741 Number of primes of the form k+1 where k is coprime to n, k < n. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A229944 A218533 A328578 * A285577 A324392 A029234

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 21 02:02 EST 2020. Contains 332086 sequences. (Running on oeis4.)