

A102380


Irregular triangle read by rows in which row n lists prime factors (with multiplicity) of the repunit (10^n  1)/9 (A002275(n)).


11



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

1,2


COMMENTS

See A003020 for other links and references.


LINKS

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), 2228.


EXAMPLE

First rows are:
1;
11;
3, 37;
11, 101;
41, 271;
3, 7, 11, 13, 37;
239, 4649;
...


MAPLE

[seq( ifactor((10^n1)/9), n=1..20)];


CROSSREFS

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


KEYWORD

nonn,tabf


AUTHOR

N. J. A. Sloane, Nov 28 2006


STATUS

approved



