Find adjacent primes which differ by a square integer: Difference between revisions
Find adjacent primes which differ by a square integer (view source)
Revision as of 14:32, 21 November 2021
, 2 years agoAdded Algol 68
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<br>Find adjacent primes under '''1,000,000''' whose difference '''(> 36)''' is a square integer.
<br><br>
=={{header|ALGOL 68}}==
{{libheader|ALGOL 68-primes}}
<lang algol68>BEGIN # find a adjacent primes where the primes differ by a square > 36 #
INT min diff = 37;
INT max prime = 1 000 000;
PR read "primes.incl.a68" PR
# form a list of primes to max prime #
[]INT prime = EXTRACTPRIMESUPTO max prime FROMPRIMESIEVE PRIMESIEVE max prime;
# construct a table of squares, we will need at most the square root of max prime #
# but in reality much less than that - assume 1000 will be enough #
[ 1 : 1000 ]BOOL is square;
FOR i TO UPB is square DO is square[ i ] := FALSE OD;
FOR i WHILE INT i2 = i * i;
i * i <= UPB is square
DO
is square[ i2 ] := TRUE
OD;
# find the primes #
FOR p TO UPB prime - 1 DO
INT q = p + 1;
INT diff = prime[ q ] - prime[ p ];
IF diff > min diff AND is square[ diff ] THEN
print( ( whole( prime[ q ], -6 ), " - ", whole( prime[ p ], -6 ), " = ", whole( diff, 0 ), newline ) )
FI
OD
END</lang>
{{out}}
<pre>
89753 - 89689 = 64
107441 - 107377 = 64
288647 - 288583 = 64
368021 - 367957 = 64
381167 - 381103 = 64
396833 - 396733 = 100
400823 - 400759 = 64
445427 - 445363 = 64
623171 - 623107 = 64
625763 - 625699 = 64
637067 - 637003 = 64
710777 - 710713 = 64
725273 - 725209 = 64
779477 - 779413 = 64
801947 - 801883 = 64
803813 - 803749 = 64
821741 - 821677 = 64
832583 - 832519 = 64
838349 - 838249 = 100
844841 - 844777 = 64
883871 - 883807 = 64
912167 - 912103 = 64
919511 - 919447 = 64
954827 - 954763 = 64
981887 - 981823 = 64
997877 - 997813 = 64
</pre>
=={{header|C}}==
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