A260589 Irregular table read by rows: n-th row lists the prime factors of A173426(n), with repetition.

11, 11, 3, 3, 37, 37, 11, 11, 101, 101, 41, 41, 271, 271, 3, 3, 7, 7, 11, 11, 13, 13, 37, 37, 239, 239, 4649, 4649, 11, 11, 73, 73, 101, 101, 137, 137, 3, 3, 3, 3, 37, 37, 333667, 333667, 12345678910987654321, 7, 17636684157301569664903, 3, 3, 7, 7, 2799473675762179389994681, 1109, 4729

Offset

1,1

Comments

Row lengths are given by A260588(n). In particular, row n = 1 would have length 0, i.e., no element, because A173426(1) = 1 has no prime factors. Therefore the sequence can be considered to start with row n = 2. (The offset refers to the k-th element of the "flattened" sequence.)

For n = 1 through n = 9, A173426(n) is the square of the repunit 1...1 of length n, therefore every prime factor appears twice. This is no longer the case for n > 9.

Links

M. F. Hasler, Table of k, a(k) for k = 1..150 (Rows n = 2 through 30, flattened.)

M. F. Hasler, Factorization of A173426 = 123...321, OEIS wiki, July 2015.

Formula

n | A173426(n) | factors = n-th row of this table

1 | 1 | []

2 | 121 | [11, 11]

3 | 12321 | [3, 3, 37, 37]

4 | 1234321 | [11, 11, 101, 101]

5 | 123454321 | [41, 41, 271, 271]

6 | 12345654321 | [3, 3, 7, 7, 11, 11, 13, 13, 37, 37]

Prog

(PARI) A260589_row(n)=A027746_row(A173426(n))
(PARI) vector(30, n, A027746_row(A173426(n))) \\ You may concat() this.

Crossrefs

Cf. A001222, A075023, A075024, A173426, A260587, A260588.

Sequence in context: A268915 A332731 A322270 * A291367 A061186 A135684

Adjacent sequences: A260586 A260587 A260588 * A260590 A260591 A260592

Keyword

nonn,tabf,base

Author

M. F. Hasler, Jul 29 2015

Status

approved