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A162325 a(n) = the largest divisor of n such that this and every smaller divisor of n are all coprime to each other. 1
1, 2, 3, 2, 5, 3, 7, 2, 3, 5, 11, 3, 13, 7, 5, 2, 17, 3, 19, 2, 7, 11, 23, 3, 5, 13, 3, 2, 29, 5, 31, 2, 11, 17, 7, 3, 37, 19, 13, 2, 41, 3, 43, 2, 5, 23, 47, 3, 7, 5, 17, 2, 53, 3, 11, 2, 19, 29, 59, 3, 61, 31, 7, 2, 13, 3, 67, 2, 23, 7, 71, 3, 73, 37, 5, 2, 11, 3, 79, 2, 3, 41, 83, 3, 17, 43, 29 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = a prime for every n >= 2.

LINKS

Table of n, a(n) for n=1..87.

EXAMPLE

The divisors of 28 are 1,2,4,7,14,28. Since 4 is not coprime with 2, but 2 is coprime with 1, then a(28) = 2.

MAPLE

with(numtheory): a:= proc(n) local l, j, s, h, k; l:= sort([divisors(n)[]]); s:= nops(l); for k while k<=s do h:= k; for j from k+1 to s do if igcd(l[k], l[j])=1 then h:=j else break fi od; s:= h od; l[s] end: seq(a(n), n=1..100); # Alois P. Heinz, Aug 04 2009

CROSSREFS

Sequence in context: A180506 A273283 A276440 * A197862 A006530 A102095

Adjacent sequences:  A162322 A162323 A162324 * A162326 A162327 A162328

KEYWORD

nonn

AUTHOR

Leroy Quet, Jul 01 2009, Jul 23 2009

EXTENSIONS

More terms from Alois P. Heinz, Aug 04 2009

STATUS

approved

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Last modified December 14 09:49 EST 2018. Contains 318095 sequences. (Running on oeis4.)