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A020250 Strong pseudoprimes to base 24. 1
25, 175, 553, 949, 1541, 1975, 2701, 4537, 6931, 7501, 13825, 21349, 25273, 25477, 29341, 38323, 42121, 42127, 47617, 49141, 52417, 63701, 80137, 83333, 85609, 94753, 105121, 113527, 128143, 144841, 167869, 169027, 179521, 181351, 197209, 201373 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. J. Mathar, Table of n, a(n) for n = 1..203

Index entries for sequences related to pseudoprimes

MATHEMATICA

strongPseudoprimeQ[b_, n_] := Module[{rems = Table[PowerMod[b, (n - 1)/2^expo, n], {expo, 0, IntegerExponent[n - 1, 2]}]}, (rems[[-1]] == 1 || MemberQ[rems, n - 1]) && PowerMod[b, n - 1, n] == 1]; max = 5000; Select[Complement[Range[2, max], Prime[Range[PrimePi[max]]]], strongPseudoprimeQ[24, #] &] (* Alonso del Arte, Aug 03 2018 *)

PROG

(PARI) is(n, a=24)= (bittest(n, 0) && !isprime(n) && n>8) || return; my(s=valuation(n-1, 2)); if(1==a=Mod(a, n)^(n>>s), return(1)); while(a!=-1 && s--, a=a^2); a==-1 \\ Felix Fröhlich, Aug 03 2018, adapted from code by M. F. Hasler in A001262

CROSSREFS

Sequence in context: A115330 A213546 A145964 * A201089 A020277 A200671

Adjacent sequences:  A020247 A020248 A020249 * A020251 A020252 A020253

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified October 24 02:02 EDT 2021. Contains 348217 sequences. (Running on oeis4.)