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A080008
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={-1,0}.
1
1, 0, 0, 1, 2, 2, 3, 5, 11, 15, 24, 40, 68, 110, 177, 290, 480, 783, 1278, 2090, 3427, 5609, 9171, 15005, 24564, 40200, 65776, 107628, 176137, 288244, 471676, 771845, 1263074, 2066938, 3382367, 5534941, 9057495, 14821891, 24254820, 39691008
OFFSET
0,5
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
Recurrence: a(n) = a(n-2)+a(n-3)+2*a(n-4)+2*a(n-5)-a(n-7)-a(n-9)-a(n-10).
G.f.: -(x^5+x^2-1)/((x^9+x^6-x^5-x^4-x^3-x+1)*(x+1))
KEYWORD
nonn
AUTHOR
Vladimir Baltic, Feb 10 2003
STATUS
approved