%N Numbers n such that the concatenation of the decimal numbers 1 through n, but omitting 5, is a prime.
%C The corresponding primes are the primes in A262575.
%C The actual values of a(1) to a(4) are also primes, although that is not a necessary condition for a number to belong to this sequence. Not all the terms of A262300 are primes, for example.
%C Probabilistic arguments suggest the sequence is infinite.
%C a(5) > 10000. - _Robert Price_, Nov 03 2018
%e The first two terms correspond to the primes 123467891011 and 123467891011121314151617.
%e a(3) corresponds to a 362-digit prime, a(4) to a 13416-digit probable prime. These two terms were found by _David Broadhurst_ on Oct 08 2015.
%Y Cf. A262575, A262300, A007908.
%A _N. J. A. Sloane_, Oct 09 2015