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!)
A140888 Number of nonprimes in [210n - 210, 210n] coprime to 210. 0
6, 13, 15, 16, 18, 19, 21, 17, 21, 21, 22, 23, 18, 22, 26, 21, 22, 21, 24, 24, 22, 25, 22, 22, 26, 24, 22, 21, 28, 23, 25, 23, 25, 24, 26, 25, 22, 27, 27, 24, 27, 22, 24, 25, 23, 26, 23, 28, 23, 26, 27, 26, 27, 26, 27, 30, 22, 26, 27, 22, 25, 24, 26, 29, 27, 24, 27, 31, 25, 26 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For almost all n, a(n) = phi(210) = 48. It first attains this value at a(1751794).

LINKS

Table of n, a(n) for n=1..70.

EXAMPLE

{1,11,13,...,209,} are coprime to 210 in [0, 210]; the nonprimes are {1,121,143,169,187,209} so a(1) = 1.

PROG

(PARI) a(n)=sum(k=210*n-210, 210*n, gcd(k, 210)==1&!isprime(k))

CROSSREFS

Cf. A008364, A140887.

Sequence in context: A031113 A112610 A100205 * A053753 A228380 A090068

Adjacent sequences:  A140885 A140886 A140887 * A140889 A140890 A140891

KEYWORD

nonn,easy,less

AUTHOR

Juri-Stepan Gerasimov, Jul 06 2008

EXTENSIONS

Corrected and rewritten by Charles R Greathouse IV, Mar 26 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 28 13:47 EST 2021. Contains 349413 sequences. (Running on oeis4.)