2-Jul-1995, corrected 26-Jul-1995
Unsolved Problem 27:
Are there integers n and x (with n>7)
such that n!=x^2-1?
By n! we mean the product of the integers from 1 to n.
It is known that 4!+1=25=5^2, 5!+1=121=11^2, and
7!+1=5041=71^2.
Reference:
- [Gardner 1978]
- Martin Gardner,
Mathematical Magic Show.
Vintage Books. New York: 1978.
Page 60.
Factorials that are one less than a Square
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