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

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A095972 Number of quadratic nonresidues modulo n. 10
0, 0, 1, 2, 2, 2, 3, 5, 5, 4, 5, 8, 6, 6, 9, 12, 8, 10, 9, 14, 13, 10, 11, 18, 14, 12, 16, 20, 14, 18, 15, 25, 21, 16, 23, 28, 18, 18, 25, 31, 20, 26, 21, 32, 33, 22, 23, 40, 27, 28, 33, 38, 26, 32, 37, 44, 37, 28, 29, 48, 30, 30, 47, 52, 44, 42, 33, 50, 45, 46, 35, 60, 36, 36, 53 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

A218578(n) is the number of times n occurs in this sequence. - Dmitri Kamenetsky, Nov 03 2012

LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Quadratic Nonresidue

FORMULA

a(n) = n - A000224(n). - R. J. Mathar, Nov 05 2012

MAPLE

A095972 := proc(n)

    local a, q;

    a := 0 ;

    for q from 0 to n-1 do

        if numtheory[quadres](q, n) = -1 then

            a := a+1 ;

        end if;

    end do;

    a ;

end proc: # R. J. Mathar, Nov 05 2012

MATHEMATICA

Table[Length[Complement[Range[n-1], Union[Mod[Range[n]^2, n]]]], {n, 100}] (* T. D. Noe, Nov 06 2012 *)

PROG

(PARI) A095972(n)={local(v); v=vector(n, i, 1); for(i=0, floor(n/2), v[i^2%n+1]=0); sum(i=1, n, v[i])} \\ Michael B. Porter, Apr 30 2010

(PARI) a(n)=my(f=factor(n)); n-prod(i=1, #f[, 1], if(f[i, 1]==2, 2^f[1, 2]\6+2, f[i, 1]^(f[i, 2]+1)\(2*f[i, 1]+2)+1)) \\ Charles R Greathouse IV, Jul 15 2011

CROSSREFS

Cf. A096013, A218578.

Sequence in context: A304718 A036355 A228390 * A091974 A029073 A058618

Adjacent sequences:  A095969 A095970 A095971 * A095973 A095974 A095975

KEYWORD

nonn

AUTHOR

Cino Hilliard, Jul 21 2004

EXTENSIONS

Edited by Don Reble, May 07 2006

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 January 15 20:47 EST 2019. Contains 319184 sequences. (Running on oeis4.)