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A066984 a(n) = gcd(prime(n+1) - 1, prime(n) + 1). 1
1, 4, 6, 2, 12, 2, 18, 2, 4, 30, 4, 2, 42, 2, 4, 2, 60, 2, 2, 72, 2, 2, 4, 6, 2, 102, 2, 108, 2, 6, 2, 4, 138, 4, 150, 4, 2, 2, 4, 2, 180, 2, 192, 2, 198, 10, 2, 2, 228, 2, 2, 240, 2, 4, 2, 4, 270, 4, 2, 282, 4, 6, 2, 312, 2, 6, 4, 2, 348, 2, 2, 6, 4, 2, 2, 4, 6, 2, 6, 2, 420, 2, 432, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

MATHEMATICA

GCD[#[[1]]+1, #[[2]]-1]&/@Partition[Prime[Range[90]], 2, 1] (* Harvey P. Dale, May 16 2021 *)

PROG

(PARI) { for (n=1, 1000, write("b066984.txt", n, " ", gcd(prime(n+1) - 1, prime(n) + 1)) ) } \\ Harry J. Smith, Apr 15 2010

CROSSREFS

Sequence in context: A118967 A256508 A059030 * A241341 A085595 A173458

Adjacent sequences:  A066981 A066982 A066983 * A066985 A066986 A066987

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Jan 27 2002

STATUS

approved

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Last modified October 28 16:09 EDT 2021. Contains 348329 sequences. (Running on oeis4.)