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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A048864 Number of nonprime numbers (composites and 1) in the reduced residue system of n. 12
1, 1, 1, 1, 2, 1, 3, 1, 3, 2, 6, 1, 7, 2, 4, 3, 10, 1, 11, 2, 6, 4, 14, 1, 12, 5, 10, 5, 19, 1, 20, 6, 11, 7, 15, 3, 25, 8, 14, 6, 28, 2, 29, 8, 12, 10, 32, 3, 28, 7, 19, 11, 37, 4, 26, 10, 22, 14, 42, 2, 43, 14, 20, 15, 32, 5, 48, 15, 27, 8, 51, 6, 52, 17, 21, 17, 41, 6, 57, 12, 33, 20 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Differs from A039776 at n = 20, 21, ...

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

FORMULA

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

a(n) = A000010(n) -( A000720(n)-A001221(n) ).

EXAMPLE

At n=100, phi(100) = 40, phi(100)-( Pi(100)-A001221(100) )=17, thus a(100) = 17.

MAPLE

A048864 := n -> nops(select(k->gcd(k, n)=1, remove(isprime, [$1..n]))); # Peter Luschny, Oct 22 2010

MATHEMATICA

Array[EulerPhi@ # - (PrimePi@ # - PrimeNu@ #) &, 82] (* Michael De Vlieger, Jul 03 2016 *)

CROSSREFS

Cf. A039776, A000010, A000720, A001221.

Sequence in context: A230070 A224762 A039776 * A003139 A244797 A145652

Adjacent sequences:  A048861 A048862 A048863 * A048865 A048866 A048867

KEYWORD

nonn

AUTHOR

Labos Elemer

EXTENSIONS

Converted second formula to an equation, added commas to the example - R. J. Mathar, Oct 23 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 March 29 14:58 EDT 2017. Contains 284270 sequences.