Left-Truncatable Primes

A left-truncatable prime is a prime number (without the digit zero) that when you remove any of its left most decimal digit, it still represents a prime number (or no number at all if you remove all of the digits). 5167 is a left-truncatable because 5167, 167, 67, and 7 are all prime.

Notes from my UBASIC program LEFT-TU.UB:

   10   ' Start of file Left-Tru.UB  Left-truncatable primes in UBASIC
   20   '
   30   word -10:cls:print
   40   print " Left-Tru.UB - Computes all left-truncatable primes (LTP)"
   50   print " Version 1.10, last revised: 2007-11-13"
   60   print " Copyright (c) 1981-2007 by author: Harry J. Smith,"
   70   print " 19628 Via Monte Dr., Saratoga CA 95070.  All rights reserved."
   80   print
   90   print " Quote from WEB page"
  100   print " www.utm.edu/research/primes/glossary/LeftTruncatablePrime.html"
  110   print
  120   print " 'Left-truncatable primes (or just truncatable primes) are"
  130   print " prime numbers (without the digit zero) that remain prime no"
  140   print " matter how many of the leading digits are omitted. For"
  150   print " example, 4632647 is left-truncatable because it and each of"
  160   print " its truncations: 632647, 32647, 2647, 647, 47, and 7 are"
  170   print " prime. We omit the digit zero to avoid trivial examples such"
  180   print " as the prime 10^60+7:"
  190   print
  200   print " 1000000000000000000000000000000000000000000000000000000000007."
  210   print
  220   print " Each of its truncations is the prime 7.'"
  230   print
  240   print " Will write file Left-Tru.OUT"
  250   strinput " Do you wish to continue (Y/N) :";S$
  260   if (S$<>"Y") and (S$<>"y") then end
  270   print
  280   '
  290   ' Computes all left-truncatable primes and outputs to file Left-Tru.Out
  300   '

{
  fileO="b132394.txt";
  v=vector(4260);
  v[1]=2;
  v[2]=3;
  v[3]=5;
  v[4]=7;
  i=0;
  j=4;
  write(fileO, "1 2");
  write(fileO, "2 3");
  write(fileO, "3 5");
  write(fileO, "4 7");
  until (i>=j,
    i++;
    p=v[i];
    P10=10^(1 + log(p)\log(10));
    for (k=1, 9,
      z=k*P10+p;
      if (isprime(z),
        j++;
        v[j]=z;
        write(fileO, j, " ", z);
      )
    )
  );
}