[seqfan] Re: A true Mac Mahon ruler?
franktaw at netscape.net
Tue Jun 25 21:13:26 CEST 2019
If a ruler can measure each distance between 1 and n exactly once, n must be a triangular number.
Franklin T. Adams-Watters
From: Éric Angelini <eric.angelini at skynet.be>
To: Sequence Discussion list <seqfan at list.seqfan.eu>
Sent: Tue, Jun 25, 2019 1:00 pm
Subject: [seqfan] A true Mac Mahon ruler?
The first 8 terms of A002049 are:
1,3,7,12,20,30,44 and 59.
I see that I can measure 29 in two
ways with this ruler (I thought only
one way was authorized):
I am obviously missing smthg as this
is an ancient seq. signed by Neil himself.
Anyway -- is it possible to build a
wooden ruler with as few as possible
vertical marks such that all integers
measures between 1 and 200 can
be materialized only once?
I guess this sort of question is as
old as the hat I'm wearing right now to
avoid the killer sun we currently have
in Brussels. Forgive me.
(and if this seq is already
in the OEIS, my shame will
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