Giuga numbers: Difference between revisions
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(Added Algol 68) |
(→{{header|ALGOL 68}}: Must spell Giuga correctly) |
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=={{header|ALGOL 68}}== |
=={{header|ALGOL 68}}== |
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<syntaxhighlight lang="algol68"> |
<syntaxhighlight lang="algol68"> |
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BEGIN # find some |
BEGIN # find some Giuga numbers, composites n such that all their distinct # |
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# prime factors f exactly divide ( n / f ) - 1 # |
# prime factors f exactly divide ( n / f ) - 1 # |
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# find the first four |
# find the first four Giuga numbers # |
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INT g count := 0; |
INT g count := 0; |
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FOR n FROM 2 WHILE g count < 4 DO |
FOR n FROM 2 WHILE g count < 4 DO |
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INT v := n; |
INT v := n; |
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BOOL is |
BOOL is giuga := TRUE; |
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INT f count := 0; |
INT f count := 0; |
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IF NOT ODD v THEN |
IF NOT ODD v THEN |
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# 2 is a prime factor of n # |
# 2 is a prime factor of n # |
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is |
is giuga := ( ( n OVER 2 ) - 1 ) MOD 2 = 0; |
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IF is |
IF is giuga THEN |
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f count +:= 1; |
f count +:= 1; |
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WHILE v MOD 2 = 0 DO v OVERAB 2 OD |
WHILE v MOD 2 = 0 DO v OVERAB 2 OD |
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FI |
FI |
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FI; |
FI; |
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IF is |
IF is giuga THEN |
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FOR f FROM 3 BY 2 WHILE f <= v AND is |
FOR f FROM 3 BY 2 WHILE f <= v AND is giuga DO |
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IF v MOD f = 0 THEN |
IF v MOD f = 0 THEN |
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# have a prime factor # |
# have a prime factor # |
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f count +:= 1; |
f count +:= 1; |
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is |
is giuga := ( ( n OVER f ) - 1 ) MOD f = 0; |
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IF is |
IF is giuga THEN |
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# n is still a candidate # |
# n is still a candidate # |
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v OVERAB f; |
v OVERAB f; |
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FI |
FI |
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OD; |
OD; |
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IF is |
IF is giuga THEN |
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# n is still a candidate, check it is not prime # |
# n is still a candidate, check it is not prime # |
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is |
is giuga := f count > 1 |
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FI |
FI |
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FI; |
FI; |
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IF is |
IF is giuga THEN |
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g count +:= 1; |
g count +:= 1; |
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print( ( " ", whole( n, 0 ) ) ) |
print( ( " ", whole( n, 0 ) ) ) |
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