Table of n, a(n) for n=1..6.
While the very first concatenation is divisible by 23, 23^2 does not divide any such number until 5861 is adjoined.
Cf. A183194, A185656, and those following.
Sequence in context: A249511 A248506 A034317 * A187879 A325052 A283019
Adjacent sequences: A185668 A185669 A185670 * A185672 A185673 A185674
James G. Merickel, Feb 01 2011