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 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: A036355 A228390 A309256 * 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

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Last modified June 13 05:29 EDT 2021. Contains 344981 sequences. (Running on oeis4.)