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A091442
Table (by antidiagonals) of permutations of two types of objects such that each cycle contains at least one object of each type. Each type of object is unlabeled.
0
1, 1, 1, 1, 3, 1, 1, 3, 3, 1, 1, 5, 8, 5, 1, 1, 5, 11, 11, 5, 1, 1, 7, 17, 26, 17, 7, 1, 1, 7, 24, 40, 40, 24, 7, 1, 1, 9, 31, 66, 85, 66, 31, 9, 1, 1, 9, 39, 95, 146, 146, 95, 39, 9, 1, 1, 11, 50, 139, 245, 304, 245, 139, 50, 11, 1, 1, 11, 59, 183, 379, 538, 538, 379, 183, 59, 11
OFFSET
1,5
REFERENCES
F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 114 (2.4.42).
FORMULA
G.f.: A(x, y) = Product_{k>=1} (1 - x^n)*(1 - y^n)/(1 - x^n - y^n).
EXAMPLE
1, 1, 1, 1, 1, ...
1, 3, 3, 5, 5, ...
1, 3, 8, 11, 17, ...
1, 5, 11, 26, 40, ...
1, 5, 17, 40, 85, ...
CROSSREFS
Sequence in context: A174546 A134444 A176149 * A025834 A257379 A336456
KEYWORD
nonn,tabl
AUTHOR
Christian G. Bower, Jan 09 2004
STATUS
approved