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A036997 Number of composite numbers <= n and relatively prime to n. 6
0, 0, 0, 0, 1, 0, 2, 0, 2, 1, 5, 0, 6, 1, 3, 2, 9, 0, 10, 1, 5, 3, 13, 0, 11, 4, 9, 4, 18, 0, 19, 5, 10, 6, 14, 2, 24, 7, 13, 5, 27, 1, 28, 7, 11, 9, 31, 2, 27, 6, 18, 10, 36, 3, 25, 9, 21, 13, 41, 1, 42, 13, 19, 14, 31, 4, 47, 14, 26, 7, 50, 5, 51, 16, 20, 16, 40, 5, 56, 11, 32, 19, 59, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

COMMENTS

30 is the largest number n with the property that if 1 < k < n and k is relatively prime to n, then k is prime. In other words, a(30) = 0 and if m > 30, then a(m) > 0. - Jonathan Sondow, Dec 08 2012

LINKS

Table of n, a(n) for n=1..84.

FORMULA

A048864(n) = A036997(n) + 1. - Peter Luschny, Oct 22 2010

MATHEMATICA

Table[ Count[ Select[ Range[ n ], GCD[ #, n ]===1& ], q_/; !(PrimeQ[ q ]||q===1) ], {n, 180} ]

CROSSREFS

A048597 gives the indices where A036997(n) = 0.

Sequence in context: A242691 A081082 A049785 * A116900 A254372 A196517

Adjacent sequences:  A036994 A036995 A036996 * A036998 A036999 A037000

KEYWORD

nonn

AUTHOR

Wouter Meeussen

EXTENSIONS

Minor edits by Ray Chandler, Mar 16 2010

STATUS

approved

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Last modified August 17 15:10 EDT 2017. Contains 290635 sequences.