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A292285 GCD of orders (in GF(p)) of primes dividing p-1, for odd primes p. 2
2, 4, 3, 5, 3, 8, 18, 11, 7, 1, 18, 20, 2, 23, 13, 29, 10, 22, 5, 3, 39, 41, 11, 48, 25, 17, 53, 9, 14, 7, 65, 68, 46, 37, 5, 2, 162, 83, 43, 89, 15, 19, 16, 98, 11, 35, 37, 113, 19, 29, 119, 8, 25, 16, 131, 67, 3, 23, 10, 94, 73, 1, 155, 39, 79, 15, 7, 173, 174, 88, 179, 61, 62, 378, 191, 97, 11, 25, 51, 418, 35, 43, 9, 73, 17, 112, 38, 23, 77 (list; graph; refs; listen; history; text; internal format)
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

CROSSREFS

Cf. A172058, A295975.

Sequence in context: A256751 A249484 A134017 * A163984 A283366 A048186

Adjacent sequences:  A292282 A292283 A292284 * A292286 A292287 A292288

KEYWORD

nonn,look

AUTHOR

Jeffrey Shallit, Dec 01 2017

STATUS

approved

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Last modified March 26 10:18 EDT 2019. Contains 321491 sequences. (Running on oeis4.)