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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 (list; graph; refs; listen; history; text; internal format)
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), 22-28.

EXAMPLE

First rows are:

1;

11;

3, 37;

11, 101;

41, 271;

3, 7, 11, 13, 37;

239, 4649;

...

MAPLE

[seq( ifactor((10^n-1)/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

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Last modified August 22 07:40 EDT 2019. Contains 326172 sequences. (Running on oeis4.)