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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
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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
Franz Lemmermeyer, Simerka - Quadratic Forms and Factorization, arXiv:1201.0282 [math.NT], 2011. For the 19-th row = [2071723, 5363222357].
Samuel Yates, The Mystique of Repunits, Math. Mag. 51 (1978), 22-28.
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EXAMPLE
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First rows:
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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