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A023585 Least prime divisor of 2*prime(n)-1. 1
3, 5, 3, 13, 3, 5, 3, 37, 3, 3, 61, 73, 3, 5, 3, 3, 3, 11, 7, 3, 5, 157, 3, 3, 193, 3, 5, 3, 7, 3, 11, 3, 3, 277, 3, 7, 313, 5, 3, 3, 3, 19, 3, 5, 3, 397, 421, 5, 3, 457, 3, 3, 13, 3, 3, 3, 3, 541, 7, 3, 5, 3, 613, 3, 5, 3, 661, 673, 3, 17, 3, 3, 733, 5, 757, 3, 3, 13, 3, 19, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

MATHEMATICA

FactorInteger[#][[1, 1]]&/@(2Prime[Range[90]]-1) (* Harvey P. Dale, Oct 08 2017 *)

PROG

(PARI) a(n) = factor(2*prime(n)-1)[1, 1]; \\ Michel Marcus, Oct 01 2013

CROSSREFS

Cf. A076274.

Sequence in context: A177904 A049072 A059887 * A089948 A336806 A023583

Adjacent sequences:  A023582 A023583 A023584 * A023586 A023587 A023588

KEYWORD

nonn

AUTHOR

Clark Kimberling

EXTENSIONS

Definition edited by Michel Marcus, Oct 01 2013

STATUS

approved

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Last modified June 21 18:22 EDT 2021. Contains 345365 sequences. (Running on oeis4.)