Find squares n where n+1 is prime: Difference between revisions
Find squares n where n+1 is prime (view source)
Revision as of 12:01, 19 December 2021
, 2 years agoAdd C
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wrch('*N')
$)</lang>
{{out}}
<pre>1 4 16 36 100 196 256 400 576 676</pre>
=={{header|C}}==
<lang c>#include <stdio.h>
#include <stdbool.h>
#include <math.h>
#define MAX 1000
void sieve(int n, bool *prime) {
prime[0] = prime[1] = false;
for (int i=2; i<=n; i++) prime[i] = true;
for (int p=2; p*p<=n; p++)
if (prime[p])
for (int c=p*p; c<=n; c+=p) prime[c] = false;
}
bool square(int n) {
int sq = sqrt(n);
return (sq * sq == n);
}
int main() {
bool prime[MAX + 1];
sieve(MAX, prime);
for (int i=2; i<=MAX; i++) if (prime[i]) {
int sq = i-1;
if (square(sq)) printf("%d ", sq);
}
printf("\n");
return 0;
}</lang>
{{out}}
<pre>1 4 16 36 100 196 256 400 576 676</pre>
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