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A020231 Strong pseudoprimes to base 5. 20

%I #34 Nov 17 2019 09:33:07

%S 781,1541,5461,5611,7813,13021,14981,15751,24211,25351,29539,38081,

%T 40501,44801,53971,79381,100651,102311,104721,112141,121463,133141,

%U 141361,146611,195313,211951,216457,222301,251521,289081,290629,298271,315121

%N Strong pseudoprimes to base 5.

%H Amiram Eldar, <a href="/A020231/b020231.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..715 from R. J. Mathar)

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/StrongPseudoprime.html">Strong Pseudoprime</a>

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

%t nmax = 400000; sppQ[n_?EvenQ, _] := False; sppQ[n_?PrimeQ, _] := False; sppQ[n_, b_] := (s = IntegerExponent[n-1, 2]; d = (n-1)/2^s; If[ PowerMod[b, d, n] == 1, Return[True], Do[If[PowerMod[b, d*2^r, n] == n-1, Return[True]], {r, 0, s - 1}]]); A020231 = {}; n = 1; While[n < nmax, n = n+2; If[sppQ[n, 5] == True, Print[n]; AppendTo[A020231, n]]]; A020231 (* _Jean-François Alcover_, Oct 20 2011, after _R. J. Mathar_ *)

%Y Cf. A005936, A001262 (base-2 SPP), A020229 (base-3 SPP), A215568 (SPP to bases 2 & 5), A215566 (SPP to bases 3 & 5), A056915 (SPP to bases 2, 3 & 5), A074773 (SPP to bases 2, 3, 5 & 7).

%K nonn

%O 1,1

%A _David W. Wilson_

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)