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| 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 16:46
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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