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A066787 a(n) = gcd(2^n + 1, n^2 + 1). 1
1, 5, 1, 17, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 65, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 41, 1, 1, 1, 1, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 29, 1, 1, 1, 1, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 565, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n)=1 or a(n)=0 mod(5) or a(n) is a prime congruent to 1 mod(4).

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

MAPLE

A066787:=n->gcd(2^n+1, n^2+1): seq(A066787(n), n=1..100); # Wesley Ivan Hurt, Jan 03 2016

MATHEMATICA

Table[GCD[2^n + 1, n^2 + 1], {n, 100}] (* Wesley Ivan Hurt, Jan 03 2016 *)

PROG

(PARI) { for (n=1, 1000, write("b066787.txt", n, " ", gcd( 2^n + 1, n^2 + 1)) ) } \\ Harry J. Smith, Mar 25 2010

(MAGMA) [GCD(2^n+1, n^2+1) : n in [1..100]]; // Wesley Ivan Hurt, Jan 03 2016

CROSSREFS

Sequence in context: A211808 A093826 A144699 * A058352 A121755 A104174

Adjacent sequences:  A066784 A066785 A066786 * A066788 A066789 A066790

KEYWORD

nonn,easy

AUTHOR

Benoit Cloitre, Jan 18 2002

STATUS

approved

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Last modified December 3 04:22 EST 2021. Contains 349445 sequences. (Running on oeis4.)