OFFSET
2,1
LINKS
Robert Israel, Table of n, a(n) for n = 2..10000
Seva, Posting on mathoverflow.net, October 29 2014.
EXAMPLE
For n = 14, the 14th prime is 43. The prime divisors of 42 are 2, 3, 7. The orders of 2, 3, 7, respectively, in GF(43), are 14,42,6, with GCD 2.
MAPLE
with(numtheory):
a:= n-> (p-> igcd(map(x-> order(x, p), factorset(p-1))[]))(ithprime(n)):
seq(a(n), n=2..100); # Alois P. Heinz, Dec 01 2017
MATHEMATICA
a[n_] := With[{k = Prime[n]-1}, GCD @@ (MultiplicativeOrder[#, k+1]& /@ FactorInteger[k][[All, 1]])];
Table[a[n], {n, 2, 100}] (* Jean-François Alcover, Apr 30 2019 *)
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Jeffrey Shallit, Dec 01 2017
STATUS
approved