MathGroup Archive 1995

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  • Subject: [mg622] SuperPrimes
  • From: Don Piele <piele at>
  • Date: Thu, 30 Mar 1995 23:04:43 -0600 (CST)

I invite your input on a short little problem called: 

                  SUPERPRIME RIB

Butchering Farmer John's cows always yields the best prime rib.  You can 
tell prime ribs by looking at the digits lovingly stamped across them, 
one by one, by FJ and the USDA.  Farmer John ensures that a purchaser of 
his prime ribs gets really prime ribs because when sliced from the right, 
the numbers on the ribs continue to stay prime right down to the last 
rib, e.g.:

     7 3 3 1

The set of ribs 7331 is prime; the three ribs 733 are prime; the two ribs 
73 are prime, and, of course, the last rib, 7, is prime.  The number 7331 
is called a superprime of length 4.

Create a funciton superPrime[N] that accepts a number N of ribs and 
prints all the superprimes of that length.  

In[1]	superPrime[4]
Out[1]	{2333, 2339, 2393, 2399, 2579, 2939, 3119, 3137, 3733, 3739, 
         3793, 3797, 5939, 7193, 7331, 7333, 7393} 

The faster the solution the better.

Got a  Mathematica Pearl?

D. Piele

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