Composite numbers k with no single digit factors whose factors are all substrings of k: Difference between revisions

Content added Content deleted
m (→‎{{header|Free Pascal}}: added Numb2USA aka commatize)
(Added XPL0 example.)
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15,317 59,177 83,731 119,911 183,347 192,413 1,819,231 2,111,317 2,237,411 3,129,361
15,317 59,177 83,731 119,911 183,347 192,413 1,819,231 2,111,317 2,237,411 3,129,361
5,526,173 11,610,313 13,436,683 13,731,373 13,737,841 13,831,103 15,813,251 17,692,313 19,173,071 28,118,827
5,526,173 11,610,313 13,436,683 13,731,373 13,737,841 13,831,103 15,813,251 17,692,313 19,173,071 28,118,827
</pre>

=={{header|XPL0}}==
Runs in 33.6 seconds on Raspberry Pi 4.
<lang XPL0>include xpllib; \for ItoA, StrFind and RlOutC
int K, C;

proc Factor; \Show certain K factors
int L, N, F, Q;
char SA(10), SB(10);
[ItoA(K, SB);
L:= sqrt(K); \limit for speed
N:= K; F:= 3;
if (N&1) = 0 then return; \reject if 2 is a factor
loop [Q:= N/F;
if rem(0) = 0 then \found a factor, F
[if F < 10 then return; \reject if too small (3, 5, 7)
ItoA(F, SA); \reject if not a sub-string
if StrFind(SB, SA) = 0 then return;
N:= Q;
if F>N then quit; \all factors found
]
else [F:= F+2; \try next prime factor
if F>L then
[if N=K then return; \reject prime K
ItoA(N, SA); \ (it's not composite)
if StrFind(SB, SA) = 0 then return;
quit; \passed all restrictions
];
];
];
Format(9, 0);
RlOutC(0, float(K));
C:= C+1;
if rem(C/10) = 0 then CrLf(0);
];

[C:= 0; \initialize element counter
K:= 11*11; \must have at least two 2-digit composites
repeat Factor;
K:= K+2; \must be odd because all factors > 2 are odd primes
until C >= 20;
]</lang>

{{out}}
<pre>
15,317 59,177 83,731 119,911 183,347 192,413 1,819,231 2,111,317 2,237,411 3,129,361
5,526,173 11,610,313 13,436,683 13,731,373 13,737,841 13,831,103 15,813,251 17,692,313 19,173,071 28,118,827
</pre>
</pre>
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