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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
OFFSET
1,3
COMMENTS
If n is a prime, a(n) = pi(n). If n is even, a(n) = 1.
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
KEYWORD
nonn
AUTHOR
Amarnath Murthy, May 24 2004
EXTENSIONS
More terms from Keith Schneider, Jul 03 2007
STATUS
approved