|
|
A079991
|
|
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={-1,1}.
|
|
0
|
|
|
1, 1, 1, 2, 5, 13, 29, 58, 124, 280, 632, 1406, 3101, 6851, 15217, 33846, 75181, 166823, 370177, 821760, 1824620, 4051056, 8993220, 19964240, 44320545, 98393849, 218438981, 484939834, 1076573833, 2390015565, 5305896445, 11779231650
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,4
|
|
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
|
|
|
FORMULA
|
a(n) = 2*a(n-1) +3*a(n-4) +a(n-6) -8*a(n-7) -a(n-8) -3*a(n-10) +2*a(n-13) +a(n-14).
G.f.: -(x^8+x^7-x^6-2*x^4-x^2-x+1)/(x^14+2*x^13-3*x^10-x^8-8*x^7+x^6+3*x^4+2*x-1).
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|