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A102380
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Irregular triangle read by rows in which row n lists prime factors (with multiplicity) of the repunit (10^n - 1)/9 (A002275(n)).
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11
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1, 11, 3, 37, 11, 101, 41, 271, 3, 7, 11, 13, 37, 239, 4649, 11, 73, 101, 137, 3, 3, 37, 333667, 11, 41, 271, 9091, 21649, 513239, 3, 7, 11, 13, 37, 101, 9901, 53, 79, 265371653, 11, 239, 4649, 909091, 3, 31, 37, 41, 271, 2906161, 11, 17, 73, 101
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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See A003020 for other links and references.
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LINKS
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Ray Chandler, Rows n=1..322, flattened (first 100 rows from T. D. Noe)
Makoto Kamada, Factorizations of 11...11 (repunit).
Yousuke Koide, Factorizations of Repunit Numbers
Samuel Yates, The Mystique of Repunits, Math. Mag. 51 (1978), 22-28.
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EXAMPLE
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First rows are:
1;
11;
3, 37;
11, 101;
41, 271;
3, 7, 11, 13, 37;
239, 4649;
...
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MAPLE
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[seq( ifactor((10^n-1)/9), n=1..20)];
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CROSSREFS
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Cf. A002275, A067063, A003020, A204845, A204846, A204847, A204848.
Sequence in context: A087100 A298256 A298927 * A204845 A260597 A147555
Adjacent sequences: A102377 A102378 A102379 * A102381 A102382 A102383
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KEYWORD
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nonn,tabf
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AUTHOR
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N. J. A. Sloane, Nov 28 2006
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STATUS
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approved
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