A260524 Pseudoprimes to bases 2, 3, 5 and 7 that are congruent to 5 (modulo 6) but are not Carmichael numbers (A002997).

468950021, 493108481, 659846021, 5936122901, 8144063621, 11408333333, 12601267541, 14252656133, 18074903681, 27223783841, 30633711701, 31093792133, 31797754721, 61426533761, 65085388961, 86610942881, 91945013333, 92380393121, 102538073177

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Mathematica

fQ[n_] := !PrimeQ[n] && PowerMod[2, n - 1, n] == 1 &&
> PowerMod[3, n - 1, n] == 1 && PowerMod[5, n - 1, n] == 1 && PowerMod[7, n - 1, n] == 1 && Mod[n, CarmichaelLambda[n]] != 1; k = 1; lst = {}; While[k < 25000000001, If[ fQ@ k, AppendTo[lst, k]; Print@ k]; k += 6]; lst

Prog

(PARI) Korselt(n)=my(f=factor(n)); for(i=1, #f[, 1], if(f[i, 2]>1||(n-1)%(f[i, 1]-1), return(0))); 1
is(n)=n%6==5 && Mod(2, n)^n==2 && Mod(3, n)^n==3 && Mod(5, n)^(n-1)==1 && Mod(7, n)^(n-1)==1 && !isprime(n) && !Korselt(n) \\ Charles R Greathouse IV, Jul 29 2015
(Perl) use ntheory ":all"; foroddcomposites { say if $_%6 == 5 && is_pseudoprime($_, 2, 3, 5, 7) && $_ % carmichael_lambda($_) != 1; } 1e9; # Dana Jacobsen, Sep 07 2015

Crossrefs

Cf. A153581.

Sequence in context: A349747 A323653 A246548 * A091677 A147717 A127888

Adjacent sequences: A260521 A260522 A260523 * A260525 A260526 A260527

Keyword

nonn

Author

Ray Chandler, Artur Jasinski and Robert G. Wilson v, Jul 28 2015

Extensions

a(9)-a(19) from Charles R Greathouse IV, Jul 29 2015

Status

approved