perplexus.info :: Just Math : Curious Consecutive Cyphers II

Curious Consecutive Cyphers II (Posted on 2009-02-23)

A positive integer T is defined as a factorial tail if there exists a positive integer P such that the decimal expansion of P! ends with precisely T consecutive zeroes, and (T+1)^th digit from the right in P! is nonzero.

How many positive integers less than 1992 are not factorial tails?

Submitted by K Sengupta

Rating: 5.0000 (1 votes)

Solution: (Hide)

There are precisely 396 numbers that are not factorial tails.
For an explanation, refer to the analytical solution submitted by Jer in this location.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
re: Complete Analytic Solution -- a nit to pick	Charlie	2009-02-25 11:19:14
Complete Analytic Solution	Jer	2009-02-24 14:23:54
re(3): Computer Solution	Daniel	2009-02-23 13:10:46
re(2): Computer Solution	Charlie	2009-02-23 12:45:50
re: Computer Solution	Charlie	2009-02-23 12:32:51
computer solution	Charlie	2009-02-23 12:27:29
Computer Solution	Daniel	2009-02-23 11:55:33

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