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A058263 a(n) = gcd(prime(n) - 1, prime(n+1) - 1). 8
1, 2, 2, 2, 2, 4, 2, 2, 2, 2, 6, 4, 2, 2, 2, 2, 2, 6, 2, 2, 6, 2, 2, 8, 4, 2, 2, 2, 4, 14, 2, 2, 2, 2, 2, 6, 6, 2, 2, 2, 2, 10, 2, 4, 2, 6, 6, 2, 2, 4, 2, 2, 10, 2, 2, 2, 2, 6, 4, 2, 2, 2, 2, 2, 4, 2, 6, 2, 2, 4, 2, 2, 6, 6, 2, 2, 4, 4, 8, 2, 2, 10, 2, 6, 2, 2, 8, 4, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 18, 6, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = gcd(A006093(n), A006093(n+1)).

EXAMPLE

a(24) = gcd(89-1, 97-1) = gcd(88, 96) = 8.

MATHEMATICA

Table[GCD[# - 1, NextPrime@ # - 1] &@ Prime@ n, {n, 102}] (* Michael De Vlieger, Dec 31 2016 *)

GCD[#[[1]], #[[2]]]&/@Partition[Prime[Range[110]]-1, 2, 1] (* Harvey P. Dale, Aug 26 2020 *)

PROG

(PARI) a(n) = gcd(prime(n)-1, prime(n+1)-1); \\ Michel Marcus, Dec 11 2013

CROSSREFS

Cf. A006093.

Sequence in context: A053238 A227783 A216321 * A232398 A048669 A158522

Adjacent sequences:  A058260 A058261 A058262 * A058264 A058265 A058266

KEYWORD

nonn

AUTHOR

Labos Elemer, Dec 06 2000

EXTENSIONS

Offset corrected to 1 by Michel Marcus, Dec 11 2013

STATUS

approved

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Last modified October 22 14:40 EDT 2021. Contains 348170 sequences. (Running on oeis4.)