How to resolve the algorithm Emirp primes step by step in the Stata programming language
Published on 12 May 2024 09:40 PM
How to resolve the algorithm Emirp primes step by step in the Stata programming language
Table of Contents
Problem Statement
An emirp (prime spelled backwards) are primes that when reversed (in their decimal representation) are a different prime. (This rules out palindromic primes.)
In each list, the numbers should be in order. Invoke the (same) program once per task requirement, this will show what limit is used as the upper bound for calculating surplus (regular) primes. The specific method of how to determine if a range or if specific values are to be shown will be left to the programmer.
Let's start with the solution:
Step by Step solution about How to resolve the algorithm Emirp primes step by step in the Stata programming language
Source code in the stata programming language
emirp 1000
list in 1/20, noobs noh
+-----+
| 13 |
| 17 |
| 31 |
| 37 |
| 71 |
|-----|
| 73 |
| 79 |
| 97 |
| 107 |
| 113 |
|-----|
| 149 |
| 157 |
| 167 |
| 179 |
| 199 |
|-----|
| 311 |
| 337 |
| 347 |
| 359 |
| 389 |
+-----+
emirp 10000
list if 7700<p & p<8000, noobs noh
+------+
| 7717 |
| 7757 |
| 7817 |
| 7841 |
| 7867 |
|------|
| 7879 |
| 7901 |
| 7927 |
| 7949 |
| 7951 |
|------|
| 7963 |
+------+
emirp 1000000
list if _n==10000, noobs noh
+--------+
| 948349 |
+--------+
program emirp
args n
qui clear
qui mata: build(`n')
qui save temp, replace
qui replace p=real(strreverse(strofreal(p)))
qui merge 1:1 p using temp, keep(3) nogen
qui drop if real(strreverse(strofreal(p)))==p
end
mata
real colvector sieve(real scalar n) {
real colvector a
real scalar i,j
if (n<2) return(J(0,1,.))
a=J(n,1,1)
a[1]=0
for (i=1; i<=n; i++) {
if (a[i]) {
j=i*i
if (j>n) return(select(1::n,a))
for (; j<=n; j=j+i) a[j]=0
}
}
}
function build(n) {
a=sieve(n)
st_addobs(rows(a))
st_addvar("long","p")
st_store(.,1,a)
}
end
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