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A079976 G.f.: 1/(1-x-x^2-x^4-x^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 (list; graph; refs; listen; history; text; internal format)
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. 755-770. North-Holland, 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), 119-135

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

FORMULA

a(n) = a(n-1)+a(n-2)+a(n-4)+a(n-5).

CROSSREFS

Cf. A002524-A002529, A072827, A072850-A072856, A079955-A080014.

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

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Last modified March 26 10:42 EDT 2017. Contains 284111 sequences.