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%I A020175 #15 Sep 27 2023 13:52:34
%S A020175 46,65,69,85,221,259,341,345,427,481,506,561,645,703,721,793,805,874,
%T A020175 897,946,1105,1173,1426,1581,1649,1702,1729,1771,1891,2257,2465,2737,
%U A020175 2806,2821,3145,3201,3811,4301,4485,5185,5461,5865,6283,6305,6601,6943,8911
%N A020175 Pseudoprimes to base 47.
%C A020175 Composite numbers n such that 47^(n-1) == 1 (mod n).
%H A020175 R. J. Mathar, <a href="/A020175/b020175.txt">Table of n, a(n) for n=1..1163</a>
%H A020175 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>
%t A020175 base = 47; t = {}; n = 1; While[Length[t] < 100, n++; If[! PrimeQ[n] && PowerMod[base, n-1, n] == 1, AppendTo[t, n]]]; t (* _T. D. Noe_, Feb 21 2012 *)
%t A020175 Select[Range[9000],CompositeQ[#]&&PowerMod[47,#-1,#]==1&] (* _Harvey P. Dale_, Sep 27 2023 *)
%Y A020175 Cf. A001567 (pseudoprimes to base 2).
%K A020175 nonn
%O A020175 1,1
%A A020175 _David W. Wilson_

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