Nice primes: Difference between revisions

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 =={{header|ALGOL 68}}==
+{{libheader|ALGOL 68-primes}}
 <lang algol68>BEGIN  # find nice primes - primes whose digital root is also prime #
     INT min prime = 501;
     INT max prime = 999;
     # sieve the primes to max prime #
+    PR read "primes.incl.a68" PR
-    [ 1 : max prime ]BOOL prime;
-    prime[ 1 ] := FALSE; prime[ 2 ] := TRUE;
+    []BOOL prime = PRIMESIEVE max prime;
-    FOR i FROM 3 BY 2 TO UPB prime DO prime[ i ] := TRUE  OD;
-    FOR i FROM 4 BY 2 TO UPB prime DO prime[ i ] := FALSE OD;
-    FOR i FROM 3 BY 2 TO ENTIER sqrt( max prime ) DO
-        IF prime[ i ] THEN FOR s FROM i * i BY i + i TO UPB prime DO prime[ s ] := FALSE OD FI
-    OD;
     # find the nice primes #
     INT nice count := 0;