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A260589 Irregular table read by rows: n-th row lists the prime factors of A173426(n), with repetition. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 9 17:35 EDT 2020. Contains 333361 sequences. (Running on oeis4.)