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Harvey P. Dale, <a href="/A227868/b227868_1.txt">Table of n, a(n) for n = 1..2000</a>
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Harvey P. Dale, <a href="/A227868/b227868_1.txt">Table of n, a(n) for n = 1..2000</a>
approved
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editing
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Select[Range[2000], CompositeQ[#]&&MemberQ[{7, 23}, Mod[#, 30]]&] (* Harvey P. Dale, Sep 21 2024 *)
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reviewed
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proposed
reviewed
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allocated for M. F. Hasler
Composite numbers congruent to 7 or 23 (mod 30).
143, 187, 203, 217, 247, 323, 413, 427, 473, 517, 533, 623, 637, 667, 697, 713, 803, 817, 833, 847, 893, 923, 1027, 1043, 1057, 1073, 1133, 1147, 1177, 1207, 1253, 1267, 1313, 1343, 1357, 1387, 1403, 1417, 1463, 1477, 1507, 1537, 1643
1,1
It is remarkable that up to 4913, numbers congruent to 7 or 23 (mod 30) are more frequently prime than composite.
(PARI) for(p=1, 1999, setsearch([7, 23], p%30)&&!isprime(p)&&print1(p", "))
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nonn
M. F. Hasler, Nov 02 2013
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allocated for M. F. Hasler
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