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A112092 a(n) is the least prime such that the multiplicative order of 4 mod a(n) equals n. 2
3, 5, 7, 17, 11, 13, 43, 257, 19, 41, 23, 241, 2731, 29, 151, 65537, 43691, 37, 174763, 61681, 337, 397, 47, 97, 251, 53, 87211, 15790321, 59, 61, 715827883, 641, 67, 137, 71, 433, 223, 229, 79, 4278255361, 83, 1429, 431, 353, 631, 277, 283, 193, 4363953127297 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) is the minimal prime divisor of A064080(n).

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..100

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

Cf. A064080, A143663.

Sequence in context: A070846 A078683 A099863 * A031441 A078150 A276044

Adjacent sequences:  A112089 A112090 A112091 * A112093 A112094 A112095

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

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Last modified October 23 12:04 EDT 2019. Contains 328345 sequences. (Running on oeis4.)