A020250 Strong pseudoprimes to base 24.

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

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