A088799 Numbers n which are divisors of the number formed by concatenating (n-3), (n-2) and (n-1) in that order.

3, 11, 9491, 12258083, 36774249, 2159487563, 2561252691, 2723957777, 6478462689, 8171873331, 333351714587, 146217070005379, 438651210016137, 13919982618156833, 41759947854470499, 1278907806311980217974478364841

Offset: 1

Author

Chuck Seggelin, Oct 19 2003

Keywords

• base
• nonn

Comments

Apart from 11, each other term in this sequence appears to also be a factor of the number formed by concatenating (n+3), (n+2) and (n+1) in that order. All terms appear to be prime. When evaluating concat((n+3),(n+2),(n+1)) - concat((n-3),(n-2),(n-1)) for members larger than 11 the difference appears to always be a number of the form 6(0)...4(0)...2 with the same number of zeros on both sides of the 4. The member will be a prime factor of this number. By factoring numbers of the form 6(0)...4(0)...2 and testing the results, three further members of this sequence have been found: 2723957777, 1260049494294190236301929754269107568067 and 103945392111236434211250670719387720140245499. I have not included these in the list of members above as they were not arrived at through brute force as the first 4 terms were and there may be other intervening terms.

Examples

			a(3)=9491 because 9491 is a factor of 948894899490.
		

Crossrefs

Cf. A069860, A088797, A088798.

Extensions

More terms from David Wasserman, Aug 25 2005