## Discrete Mathematics & Theoretical Computer Science, Vol 7 (2005)

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DMTCS vol 7 no 1 (2005), pp. 71-74

# Discrete Mathematics & Theoretical Computer Science

## Volume 7 n° 1 (2005), pp. 71-74

author: M. D. Atkinson Some equinumerous pattern-avoiding classes of permutations Permutations, patterns, enumeration Suppose that p,q,r,s are non-negative integers with m=p+q+r+s. The class X(p,q,r,s) of permutations that contain no pattern of the form αβγ where |α|=r, |γ|=s and β is any arrangement of {1,2,…,p}∪{m-q+1, m-q+2, …,m} is considered. A recurrence relation to enumerate the permutations of X(p,q,r,s) is established. The method of proof also shows that X(p,q,r,s)=X(p,q,1,0)X(1,0,r,s) in the sense of permutational composition. 2000 MATHEMATICS SUBJECT CLASSIFICATION: 05A05 If your browser does not display the abstract correctly (because of the different mathematical symbols) you can look it up in the PostScript or PDF files. M. D. Atkinson (2005), Some equinumerous pattern-avoiding classes of permutations, Discrete Mathematics and Theoretical Computer Science 7, pp. 71-74 For a corresponding BibTeX entry, please consider our BibTeX-file. dm070106.ps.gz (47 K) dm070106.ps (110 K) dm070106.pdf (63 K)

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