A262552 Numbers n such that the concatenation of the decimal numbers 1 through n, but omitting 5, is a prime.

11, 17, 157, 3631

Offset: 1

Author

N. J. A. Sloane, Oct 09 2015

Keywords

• nonn
• base
• more

Comments

The corresponding primes are the primes in A262575.

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.

Probabilistic arguments suggest the sequence is infinite.

a(5) > 10000. - Robert Price, Nov 03 2018

Examples

			The first two terms correspond to the primes 123467891011 and 123467891011121314151617.
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.
		

Crossrefs

Cf. A262575, A262300, A007908.