OFFSET
0,6
COMMENTS
Also, number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=3, r=3, I={-2,-1,0}.
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
Index entries for linear recurrences with constant coefficients, signature (0, 1, 1, 1, 4, 4, -1, -3, -2, 1, -4, -3, 1, 4, 0, -1, 1, 1, 0, -1).
FORMULA
a(n) = a(n-2) +a(n-3) +a(n-4) +4*a(n-5) +4*a(n-6) -a(n-7) -3*a(n-8) -2*a(n-9) +a(n-10) -4*a(n-11) -3*a(n-12) +a(n-13) +4*a(n-14) -a(n-16) +a(n-17) +a(n-18) -a(n-20) .
G.f.: -(x^14-x^12 -x^11+x^9 -2*x^8+2*x^6 +x^5+x^3 +x^2-1)/( x^20 -x^18 -x^17 +x^16 -4*x^14 -x^13 +3*x^12 +4*x^11 -x^10 +2*x^9 +3*x^8 +x^7 -4*x^6 -4*x^5 -x^4 -x^3 -x^2+1).
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Baltic, Feb 17 2003
STATUS
approved