last Saturday... (maximin prime dates)
- [ trivial but maybe fun ]
Last Saturday may have been a special day in primedom.
It may have been a "maximin" prime date. At least, using the
American convention of putting the month first.
Definitions: For a date with month a and day b, define the
sequence N of all n>1 such that a*10^n+b is prime.
If N is not empty, choose the minimum n in the sequence.
Then, find the maximum over all dates of these minimal n.
The dates which yield these maxima will be called "American
maximin prime dates"
Unless N is nonempty for the 1st of October, the only American
maximin prime date is the 27th October. 10.10^n + 27 is prime for
n=82, but composite for n=2,3,4,...,81
If we similarly define "European maximin prime dates", with the
month coming at the end, then (unless N is nonempty for the 10th
of January), the only European maximin prime date is the 31st of
31.10^n + 1 is prime for n=51, but composite for n=2,3,...,50.
Do these get into the prime curios pages?? :-)
Anyone whose birthday falls on (one of) these two dates??
This email is inspired by a thread that occurred around the 4th of
Yours, Mike H...
Michael Hartley : Michael.Hartley@...
Head, Department of Information Technology,
Sepang Institute of Technology
"If you entertain a thought, it becomes an attitude..."