

A060391


If 10^n can be written as x*y where the digits of x and y are all nonzero, then let a(n) = largest such y, otherwise a(n) = 1.


1



1, 5, 25, 125, 625, 3125, 15625, 78125, 1, 1953125, 1, 1, 1, 1, 1, 1, 1, 1, 3814697265625, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 116415321826934814453125, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
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OFFSET

0,2


COMMENTS

According to Ogilvy and Anderson, 10^33 is the highest known power of ten that can be expressed as the product of two zerofree factors. "If there is another one, it is greater than 10^5000." p. 89


REFERENCES

C. Stanley Ogilvy and John T. Anderson, Excursions in Number Theory, Oxford University Press, 1966, p. 89.
Rudolph Ondrejka, Nonzero factors of 10^n, Recreational Mathematics Magazine, no. 6 (1961), p. 59.


LINKS



EXAMPLE

10^2 = 4 * 25, so a(2) = 25.


CROSSREFS



KEYWORD

sign,base


AUTHOR



STATUS

approved



