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Pseudoprimes to base 47.
1

%I #15 Sep 27 2023 13:52:34

%S 46,65,69,85,221,259,341,345,427,481,506,561,645,703,721,793,805,874,

%T 897,946,1105,1173,1426,1581,1649,1702,1729,1771,1891,2257,2465,2737,

%U 2806,2821,3145,3201,3811,4301,4485,5185,5461,5865,6283,6305,6601,6943,8911

%N Pseudoprimes to base 47.

%C Composite numbers n such that 47^(n-1) == 1 (mod n).

%H R. J. Mathar, <a href="/A020175/b020175.txt">Table of n, a(n) for n=1..1163</a>

%H <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>

%t 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 Select[Range[9000],CompositeQ[#]&&PowerMod[47,#-1,#]==1&] (* _Harvey P. Dale_, Sep 27 2023 *)

%Y Cf. A001567 (pseudoprimes to base 2).

%K nonn

%O 1,1

%A _David W. Wilson_