Download or view leftTruncatablePrimes.frink in plain text format
/** This program finds left-truncatable primes, that is, prime numbers that
always produce prime numbers when their leftmost digit is chopped off.
This builds them from a starting set of primes and will find all
left-truncatable primes. Zero is not allowed as a digit in this
formulation, which produces a finite number of solutions.
*/
testPrime[nums] :=
{
result = new array
for d = [1,2,3,4,5,6,7,8,9]
{
for n = nums
{
c = parseInt["$d$n"]
if isPrime[c] and c != 1
result.push[c]
}
}
return result
}
results = [1,2,3,5,7]
digits = 1
while (length[results] != 0)
{
newresults = new array
newresults = testPrime[results]
println["$digits\t" + length[newresults] + "\t" + newresults]
results = newresults
digits = digits + 1
}
Download or view leftTruncatablePrimes.frink in plain text format
This is a program written in the programming language Frink.
For more information, view the Frink
Documentation or see More Sample Frink Programs.
Alan Eliasen was born 20159 days, 22 hours, 59 minutes ago.