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A195153
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Irregular triangle read by rows in which row n lists numbers d-1 that do not divide n, where d divides n.
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3
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2, 3, 4, 5, 6, 3, 7, 2, 8, 4, 9, 10, 5, 11, 12, 6, 13, 2, 4, 14, 3, 7, 15, 16, 5, 8, 17, 18, 3, 9, 19, 2, 6, 20, 10, 21, 22, 5, 7, 11, 23, 4, 24, 12, 25, 2, 8, 26, 3, 6, 13, 27, 28, 4, 9, 14, 29, 30, 3, 7, 15, 31, 2, 10, 32, 16, 33, 4, 6, 34, 5, 8, 11, 17, 35
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listen;
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OFFSET
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3,1
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COMMENTS
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It appears that only rows 3, 4, 6, 8, 12, 24 have the property that all their members are primes. See the example. See also the comment at A018253.
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LINKS
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EXAMPLE
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Written as an irregular triangle:
2,
3,
4,
5,
6,
3, 7,
2, 8,
4, 9,
10,
5, 11,
12,
6, 13,
2, 4, 14,
3, 7, 15,
16,
5, 8, 17,
18,
3, 9, 19,
2, 6, 20,
10, 21,
22,
5, 7, 11, 23
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MATHEMATICA
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Flatten[Table[d = Divisors[n]; Select[Rest[d-1], Mod[n, #] > 0 &], {n, 3 , 100}]] (* T. D. Noe, Sep 23 2011 *)
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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