

A080014


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


77



1, 1, 1, 3, 6, 10, 18, 35, 65, 119, 221, 412, 764, 1416, 2629, 4881, 9057, 16807, 31194, 57894, 107442, 199399, 370065, 686799, 1274617, 2365544, 4390184, 8147680, 15121161, 28063153, 52082017, 96658283, 179386750, 332921362, 617864098
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OFFSET

0,4


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..34.
Vladimir Baltic, On the number of certain types of strongly restricted permutations, Applicable Analysis and Discrete Mathematics Vol. 4, No 1 (2010), 119135
Index entries for linear recurrences with constant coefficients, signature (1,1,1,1,1,1).


FORMULA

Recurrence: a(n) = a(n1)+a(n2)+a(n3)+a(n4)a(n5)a(n6).
G.f.: (x^21)/(x^6+x^5x^4x^3x^2x+1).


PROG

(PARI) Vec((x^21)/(x^6+x^5x^4x^3x^2x+1)+O(x^99)) \\ Charles R Greathouse IV, Jun 12 2015


CROSSREFS

Cf. A002524A002529, A072827, A072850..A072856, A079955..A080014.
Sequence in context: A261631 A029864 A075111 * A132274 A253768 A091714
Adjacent sequences: A080011 A080012 A080013 * A080015 A080016 A080017


KEYWORD

nonn,easy


AUTHOR

Vladimir Baltic, Jan 24 2003


STATUS

approved



