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

28749, 21757820799, 4373079629403

Offset: 1

Author

Giovanni Resta, Jun 17 2015

Keywords

• nonn
• more
• base
• hard
• bref

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).

Examples

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

Links

• 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.

Crossrefs

Cf. A248915.