Séminaire CAESAR
de combinatoire additive




Séance du 9 janvier 2014
(11 heures, UPMC Paris 6 Jussieu, couloir 15-16, salle 101):

Jean-Marc DESHOUILLERS
(Bordeaux)

On the density of the final non-zero digits of n!


The sequence A008904 from the On-line Encyclopedia of Integers Sequences gives the "final non-zero digit" of n! written in the base 10, studied at least some fifty years ago by Kakutani. The comments on this entry indicate that this sequence, which contains only the four digits 2, 4, 6, 8 for n>1, is an "automatic sequence" and the given computation illustrates the fact that the four above mentioned digits occur with the same frequency.
I shall present some results due to Imre Ruzsa and myself on the same question related to the base 12, where some special feature occurs. I shall also report on a joint work in progress, with Greg Dresden (W&L) and Shanta Laishram (ISI Delhi), concerning the case of a general base b.



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