A262299 Let S(n) denote the sequence formed by concatenating the decimal numbers 1,2,3,..., omitting n; a(n) is the smallest prime in S(n), or -1 if no term in S(n) is prime.

2, 13, 124567, 12356789, 123467891011, 123457, 123456891011

Offset

1,1

Comments

A262300 is now the main entry for this question.

Links

Table of n, a(n) for n=1..7.

Example

a(8) = 1234567910111213...1873 (ending at 1873, a 6384-digit probable prime, and too large to display here) was found by David Broadhurst on Sep 27 2015.
a(9) = 1234567810111213141516171819,
a(11) = 123456789101213,
and a(19) = 12345678910111213141516171820212223242526272829.
Sep 28, 2015: David Broadhurst has also found a(10), a(12), a(14), a(16), a(17), a(18), and a(20). See A262300 for their values.
a(13) is at present unknown.

Crossrefs

A262300 gives the last term in S(n) when a prime appears for the first time.

See A262571-A262582 for the sequences S(1) through S(12).

Cf. A007908 (which plays the role of S(0)).

For the primes in S(1) and S(2) see A089987, A262298.

Sequence in context: A118912 A027680 A241569 * A135970 A027738 A219221

Adjacent sequences: A262296 A262297 A262298 * A262300 A262301 A262302

Keyword

nonn,base,more

Author

N. J. A. Sloane and Jerrold B. Tunnell, Sep 25 2015

Status

approved