login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

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

License Agreements, Terms of Use, Privacy Policy .

Last modified November 18 19:06 EST 2017. Contains 294894 sequences.