A091442 - OEIS

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.

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

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OFFSET

1,5

REFERENCES

F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 114 (2.4.42).

LINKS

Table of n, a(n) for n=1..77.

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, ...