Wieferich primes: Difference between revisions
Added Algol 68
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=={{header|ALGOL 68}}==
{{works with|ALGOL 68G|Any - tested with release 2.8.3.win32}}
<syntaxhighlight lang="algol68">
BEGIN # find Wierferich Primes: primes p where p^2 evenly divides 2^(p-1)-1 #
INT max number = 5 000; # maximum number we will consider #
# set precision of LONG LONG INT - p^5000 has over 1500 digits #
PR precision 1600 PR
PR read "primes.incl.a68" PR # include prime utlities #
# get a list of primes up to max number #
[]INT prime = EXTRACTPRIMESUPTO max number
FROMPRIMESIEVE PRIMESIEVE max number;
# find the primes #
INT p pos := LWB prime;
LONG LONG INT two to p minus 1 := 1;
INT power := 0;
INT w count := 0;
WHILE w count < 2 DO
INT p = prime[ p pos ];
WHILE power < ( p - 1 ) DO
two to p minus 1 *:= 2;
power +:= 1
OD;
IF ( two to p minus 1 - 1 ) MOD ( p * p ) = 0 THEN
print( ( " ", whole( p, 0 ) ) );
w count +:= 1
FI;
p pos +:= 1
OD
END
</syntaxhighlight>
{{out}}
<pre>
1093 3511
</pre>
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