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Find prime n such that reversed n is also prime: Difference between revisions
Find prime n such that reversed n is also prime (view source)
Revision as of 14:17, 2 June 2021
, 2 years ago→{{header|Nim}}
m (→{{header|Phix}}: fixed a couple of syntax glitches, added personal tag) |
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</pre>
=={{header|Nim}}==
<lang Nim>import math, strutils
const
N1 = 499 # Limit for the primes.
N2 = 999 # Limit for the reverses of primes.
# Sieve of Erathosthenes.
var composite: array[2..N2, bool] # Default is false.
for p in 2..sqrt(N2.toFloat).int:
if not composite[p]:
for k in countup(p * p, N2, p):
composite[k] = true
template isPrime(n: int): bool = not composite[n]
func reversed(n: int): int =
var n = n
while n != 0:
result = 10 * result + n mod 10
n = n div 10
var result: seq[int]
for n in 2..N1:
if n.isPrime and reversed(n).isPrime:
result.add n
for i, n in result:
stdout.write ($n).align(3)
stdout.write if (i + 1) mod 10 == 0: '\n' else: ' '
echo()</lang>
{{out}}
<pre> 2 3 5 7 11 13 17 31 37 71
73 79 97 101 107 113 131 149 151 157
167 179 181 191 199 311 313 337 347 353
359 373 383 389 </pre>
=={{header|Perl}}==
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