

A123298


Number of incongruent restricted disjoint covering systems (IRDCS) of length n.


0



0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 4, 6, 18, 14, 26, 84, 88, 46, 176, 380, 812, 844, 1770, 2164, 5554, 9244, 25384, 62092, 68176, 85762, 304892, 855072, 1229050, 1805096
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OFFSET

1,11


COMMENTS

An IRDCS of length n is a sequence of n integers s(1),...,s(n) with the property that if s(i)=m for some m then the other members of the sequence with value m are precisely s(i+km) for all k such that i+km is in [1,n] and further such that any integer appearing in the sequence appears at least twice. For example the two IRDCS of length n are 6,9,3,4,5,3,6,4,3,5,9 and its reverse.


REFERENCES

Gerry Myerson, Jacky Poon and Jamie Simpson, Incongruent restricted disjoint covering systems, preprint.


LINKS

Table of n, a(n) for n=1..40.


CROSSREFS

Sequence in context: A213902 A170770 A107499 * A189877 A189868 A110981
Adjacent sequences: A123295 A123296 A123297 * A123299 A123300 A123301


KEYWORD

nice,nonn


AUTHOR

Jamie Simpson (simpson(AT)maths.curtin.edu.au), Jun 25 2007, corrected Sep 11 2007


STATUS

approved



