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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

138.0. "Langford Sequences" by HARE::STAN () Fri Aug 24 1984 19:46

An (m,n) Langford sequence is a sequence of integers with the following
properties:

(a) Each member of the sequence is a positive integer between 1 and n
    inclusive.

(b) Each integer k (between 1 and n) occurs m times in the sequence and
    successive occurrences are separated by k other integers.

An example of a (2,4) Langford sequence is:

	2 3 4 2 1 3 1 4   .

An example of a (3,9) Langford sequence is:

	1 9 1 6 1 8 2 5 7 2 6 9 2 5 8 4 7 6 3 5 4 9 3 8 7 4 3   .

A (4,24) Langford sequence is known.

It is not known under what circumstances an (m,n) Langford sequence exists.

	- from a talk by Dave Roselle -
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