|
Search: id:A080013
|
|
|
| A080013 |
|
Number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=2, r=2, I={0,1}. |
|
+0
1
|
|
| 1, 0, 0, 1, 1, 1, 1, 3, 3, 4, 6, 9, 12, 16, 24, 33, 46, 64, 91, 127, 177, 249, 349, 489, 684, 960, 1345, 1884, 2640, 3700, 5185, 7264, 10180, 14265, 19989, 28009, 39249, 54999, 77067, 107992, 151326
(list; graph; listen)
|
|
|
OFFSET
|
0,8
|
|
|
COMMENT
|
Also the number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=2, r=2, I={0,-1}.
|
|
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.
|
|
FORMULA
|
Recurrence: a(n) = a(n-2)+a(n-3)+a(n-4)-a(n-6) G.f.: -(x^2-1)/(x^6-x^4-x^3-x^2+1)
|
|
CROSSREFS
|
Cf. A002524..A002529, A072827, A072850..A072856, A079955..A080014.
Sequence in context: A137901 A138095 A023837 this_sequence A152949 A058660 A059871
Adjacent sequences: A080010 A080011 A080012 this_sequence A080014 A080015 A080016
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Vladimir Baltic (baltic(AT)matf.bg.ac.yu), Jan 24 2003
|
|
|
Search completed in 0.002 seconds
|
