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 A177055 Numbers k such that each decimal digit is a quadratic non-residue modulo k. 1

%I

%S 22,25,26,32,35,36,38,52,53,56,63,65,66,72,75,76,77,78,85,88,222,225,

%T 228,232,235,236,237,252,255,256,258,262,266,267,268,272,273,275,276,

%U 282,283,285,286,288,323,325,332,333,335,336,352,353,357,368,372,375,376,377,385,387,522,523,525,528,532,533,535,536

%N Numbers k such that each decimal digit is a quadratic non-residue modulo k.

%C The digits 0,1,4,9 are squares, so no members of the sequence have those digits. - _Robert Israel_, Apr 03 2017

%H Robert Israel, <a href="/A177055/b177055.txt">Table of n, a(n) for n = 1..10000</a>

%e 75 is in the sequence because neither 7 nor 5 is a square mod 75. - Corrected by _Robert Israel_, Apr 03 2017

%p isA177055 := proc(n) local d; for d in convert(n,base,10) do if numtheory[quadres](d,n) <> -1 then return false; end if; end do; return true; end proc:

%p for n from 1 to 140 do if isA177055(n) then printf("%d,",n) ; end if ; end do: # _R. J. Mathar_, Dec 12 2010

%K nonn,base,less

%O 1,1

%A _Michel Lagneau_, Dec 09 2010

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Last modified January 20 23:47 EST 2021. Contains 340332 sequences. (Running on oeis4.)