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A080007
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={0,1}.
1
1, 0, 0, 1, 2, 4, 4, 8, 19, 32, 56, 97, 180, 336, 592, 1064, 1925, 3488, 6312, 11345, 20486, 37028, 66852, 120688, 217767, 393216, 710032, 1281729, 2313896, 4177216, 7541568, 13615344, 24579657, 44374528, 80111088, 144628065, 261102474
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
a(n) = a(n-2)+2*a(n-3)+2*a(n-4)+4*a(n-5)-2*a(n-7)-a(n-8)-a(n-10).
G.f.: -(x^5+x^3+x^2-1)/(x^10+x^8+2*x^7-4*x^5-2*x^4-2*x^3-x^2+1)
KEYWORD
nonn
AUTHOR
Vladimir Baltic, Feb 10 2003
STATUS
approved