OFFSET
1,1
COMMENTS
There are no even pseudoprimes to an even base.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
a(n)=Min{x=4n-1 number; Mod[ -1+n^(x-1), x]=0}
EXAMPLE
n=1: base = 4n-1=3, smallest relevant power is -1+2^(286-1) which is divisible by 286.
Sieving further residue classes, smallest regularly arising pseudoprimes are 6,10 etc..
MATHEMATICA
a[n_] := Module[{k = 2}, While[GCD[n, k] > 1 || PrimeQ[k] || PowerMod[n, k - 1, k] != 1, k += 2]; k]; Table[a[4*n - 1], {n, 1, 100}] (* Amiram Eldar, Nov 11 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 25 2003
STATUS
approved