OFFSET
1,1
COMMENTS
a(n) is the minimal prime divisor of A064080(n).
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..1122 (first 100 terms from Amiram Eldar)
MATHEMATICA
a[n_] := Module[{f = FactorInteger[4^n - 1][[;; , 1]]}, Do[p = f[[k]]; If[ MultiplicativeOrder[4, p] == n, Break[] ], {k, 1, Length[f]}]; p]; Array[a, 100] (* Amiram Eldar, Jan 27 2019 *)
PROG
(PARI) a(n) = {my(p = 3); while (znorder(Mod(4, p)) != n, p = nextprime(p+1)); p; } \\ Michel Marcus, Feb 08 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Aug 28 2008
EXTENSIONS
a(29)-a(30) from Michel Marcus, Feb 08 2016
More term from Amiram Eldar, Jan 27 2019
STATUS
approved