Geodesic
Contravariant Functors on Finite Sets and Stirling Numbers
Theory and applications of categories, The Lambek Festschrift, Tome 6 (1999), pp. 65-76.

Voir la notice de l'article provenant de la source Theory and Applications of Categories website

We characterize the numerical functions which arise as the cardinalities of contravariant functors on finite sets, as those which have a series expansion in terms of Stirling functions. We give a procedure for calculating the coefficients in such series and a concrete test for determining whether a function is of this type. A number of examples are considered.
Classification : 18A22, 05A10.
Keywords: Functor, cardinality, Stirling numbers. 
@article{TAC_1999_6_a4,
     author = {Robert Par\'e},
     title = {Contravariant {Functors} on {Finite} {Sets} and {Stirling} {Numbers}},
     journal = {Theory and applications of categories},
     pages = {65--76},
     publisher = {mathdoc},
     volume = {6},
     year = {1999},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_1999_6_a4/}
}
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Robert Paré. Contravariant Functors on Finite Sets and Stirling Numbers. Theory and applications of categories, The Lambek Festschrift, Tome 6 (1999), pp. 65-76. http://geodesic.mathdoc.fr/item/TAC_1999_6_a4/