

A079976


G.f.: 1/(1xx^2x^4x^5).


2



1, 1, 2, 3, 6, 11, 20, 36, 65, 118, 214, 388, 703, 1274, 2309, 4185, 7585, 13747, 24915, 45156, 81841, 148329, 268832, 487232, 883061, 1600463, 2900685, 5257212, 9528190, 17268926, 31298264, 56725087, 102808753, 186330956, 337706899
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OFFSET

0,3


COMMENTS

Number of compositions of n into elements of the set {1,2,4,5}.
Number of permutations (p(1),...,p(n)) of (1..n) satisfying k<=p(i)i<=r and p(i)i not in I, i=1..n, with k=1, r=4, I={2}.


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 4 (2010), 119135
Index entries for linear recurrences with constant coefficients, signature (1,1,0,1,1)


FORMULA

a(n) = a(n1)+a(n2)+a(n4)+a(n5).


CROSSREFS

Cf. A002524A002529, A072827, A072850A072856, A079955A080014.
Sequence in context: A002985 A239342 A093608 * A017992 A018172 A018076
Adjacent sequences: A079973 A079974 A079975 * A079977 A079978 A079979


KEYWORD

nonn


AUTHOR

Vladimir Baltic, Feb 17 2003


EXTENSIONS

Since this sequence arises in several different contexts, I made the definition as simple as possible.  N. J. A. Sloane, Apr 17 2011


STATUS

approved



