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A262552 Numbers n such that the concatenation of the decimal numbers 1 through n, but omitting 5, is a prime. 2
11, 17, 157, 3631 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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.

LINKS

Table of n, a(n) for n=1..4.

EXAMPLE

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.

Sequence in context: A226677 A056577 A166655 * A279332 A286959 A146446

Adjacent sequences:  A262549 A262550 A262551 * A262553 A262554 A262555

KEYWORD

nonn,base,more

AUTHOR

N. J. A. Sloane, Oct 09 2015

STATUS

approved

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Last modified May 28 21:38 EDT 2017. Contains 287241 sequences.