OFFSET
1,1
LINKS
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
KEYWORD
nonn
AUTHOR
STATUS
approved