Permutation Of Some Primes
Jim Nastos
nastos at cs.ualberta.ca
Thu Apr 1 23:56:21 CEST 2004
On Thu, 1 Apr 2004, Leroy Quet wrote:
> I leave as a challenge, which I did myself in not too much time by
> trial-and-error and by-hand,
> find the permutation of the first 10 primes (those primes <= 29) so that
> the greatest prime divisors form a permutation of the first 9 primes
> (those primes <= 23).
Hint: there's only one way to build the primes 19 and 23, which then
imply only one way to build 11.
(Spoiler space)
Leroy,
you mention "the permutation" of the first 10 primes... did you
exhaustively show this is unique (of course, unique up to reversal of the
permuation.) I suppose with the facts I mention above, an exhaustive
search wouldn't be too hard.
The answer I got was 23 7 5 29 17 2 11 3 19 13 yielding the 10-1 distinct
primes 5 3 17 23 19 13 7 11 2
J
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