Find squares n where n+1 is prime: Difference between revisions
Find squares n where n+1 is prime (view source)
Revision as of 15:35, 22 December 2021
, 2 years agoadded AWK
Not a robot (talk | contribs) (Add Cowgol) |
Catskill549 (talk | contribs) (added AWK) |
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<pre>
1 4 16 36 100 196 256 400 576 676
</pre>
=={{header|AWK}}==
<lang AWK>
# syntax: GAWK -f FIND_SQUARES_N_WHERE_N+1_IS_PRIME.AWK
BEGIN {
start = 1
stop = 999
n = 2
n2 = n^2
printf("1")
count++
while (n2 < stop) {
if (is_prime(n2+1)) {
printf(" %d",n2)
count++
}
n += 2
n2 = n^2
}
printf("\nFind squares %d-%d: %d\n",start,stop,count)
exit(0)
}
function is_prime(n, d) {
d = 5
if (n < 2) { return(0) }
if (n % 2 == 0) { return(n == 2) }
if (n % 3 == 0) { return(n == 3) }
while (d*d <= n) {
if (n % d == 0) { return(0) }
d += 2
if (n % d == 0) { return(0) }
d += 4
}
return(1)
}
</lang>
{{out}}
<pre>
1 4 16 36 100 196 256 400 576 676
Find squares 1-999: 10
</pre>
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