A259047 Composite numbers which divide the concatenation of their prime factors, with multiplicity, in ascending order.

28749, 21757820799, 4373079629403

Offset

1,1

Comments

a(2) found by Jens Kruse Andersen who also cleverly derived 119 large terms of the sequence from the factorization of numbers of the form 10^k+1 (see Links).

10^13 < a(4) <= 7810053011863508278028459 (the smallest of J. K. Andersen's large terms).

Links

Table of n, a(n) for n=1..3.

Michael S. Branicky, Python program for Andersen's algorithm extended to arbitrary base/ordering

Carlos Rivera, Puzzle 472. What is the second solution?, The Prime Puzzles & Problems Connection.

StackExchange, New term in ascending order

Example

4373079629403 is equal to 3*367*2713*1464031 and it is a divisor of 336727131464031, hence it in the sequence.

Crossrefs

Cf. A248915.

Sequence in context: A213460 A043660 A296814 * A237321 A249957 A157610

Adjacent sequences: A259044 A259045 A259046 * A259048 A259049 A259050

Keyword

nonn,more,base,hard,bref

Author

Giovanni Resta, Jun 17 2015

Status

approved