A204846 Irregular triangle read by rows in which row n lists algebraic prime factors of the repunit (10^n - 1)/9 (A002275(n)).

1, 1, 1, 11, 1, 3, 11, 37, 1, 11, 101, 3, 37, 11, 41, 271

Offset

1,4

Links

Table of n, a(n) for n=1..16.

Samuel Yates, The Mystique of Repunits, Math. Mag. 51 (1978), 22-28.

Example

Triangle begins: 1
1
1
11
1
3,11,37
1
11,101
3,37
11,41,271
...

Crossrefs

Cf. A002275, A102380, A204845.

Sequence in context: A214676 A010198 A307245 * A127991 A110305 A010199

Adjacent sequences: A204843 A204844 A204845 * A204847 A204848 A204849

Keyword

nonn,tabf,more

Author

N. J. A. Sloane, Jan 19 2012

Status

approved