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A079963
Number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=1, r=5, I={1,2}.
0
1, 1, 1, 1, 2, 4, 7, 10, 14, 21, 34, 55, 86, 131, 200, 310, 485, 757, 1174, 1815, 2810, 4362, 6778, 10524, 16323, 25310, 39260, 60924, 94549, 146706, 227599, 353093, 547826, 850005, 1318859, 2046257, 3174775, 4925699, 7642389, 11857510
OFFSET
0,5
COMMENTS
Number of compositions (ordered partitions) of n into elements of the set {1,4,5,6}.
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
Vladimir Baltic, On the number of certain types of strongly restricted permutations, Applicable Analysis and Discrete Mathematics Vol. 4, No 1 (2010), 119-135.
FORMULA
a(n) = a(n-1)+a(n-4)+a(n-5)+a(n-6).
G.f.: -1/(x^6+x^5+x^4+x-1).
KEYWORD
nonn,easy
AUTHOR
Vladimir Baltic, Feb 19 2003
STATUS
approved