

A080000


Number of permutations satisfying k<=p(i)i<=r and p(i)i not in I, i=1..n, with k=2, r=3, I={1,1,2}.


0



1, 1, 1, 1, 1, 2, 3, 5, 7, 9, 12, 16, 24, 35, 50, 70, 96, 135, 190, 270, 383, 539, 759, 1065, 1500, 2116, 2985, 4212, 5932, 8356, 11770, 16585, 23381, 32953, 46445, 65445, 92216, 129951, 183129, 258091, 363719, 512566, 722316, 1017886, 1434445
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OFFSET

0,6


REFERENCES

D. H. Lehmer, Permutations with strongly restricted displacements. Combinatorial theory and its applications, II (Proc. Colloq., Balatonfured, 1969), pp. 755770. NorthHolland, Amsterdam, 1970.


LINKS

Table of n, a(n) for n=0..44.
Vladimir Baltic, On the number of certain types of strongly restricted permutations, Applicable Analysis and Discrete Mathematics Vol. 4, No 1 (April, 2010), 119135


FORMULA

Recurrence: a(n) = a(n1)+2*a(n5)a(n6)+a(n7)a(n10) G.f.: (x^51)/(x^10x^7+x^62*x^5x+1)


CROSSREFS

Cf. A002524A002529, A072827, A072850A072856, A079955A080014.
Sequence in context: A062438 A102424 A237826 * A032459 A263647 A028870
Adjacent sequences: A079997 A079998 A079999 * A080001 A080002 A080003


KEYWORD

nonn


AUTHOR

Vladimir Baltic, Feb 10 2003


STATUS

approved



