A262582 Concatenation of the numbers from 1 to n but omitting 12.

1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678910, 1234567891011, 123456789101113, 12345678910111314, 1234567891011131415, 123456789101113141516, 12345678910111314151617, 1234567891011131415161718, 123456789101113141516171819, 12345678910111314151617181920

Offset

1,2

Comments

The first (probable) prime in this sequence is a(960) = 1234567891011131415...961 (ending in 961), found by David Broadhurst, Sep 28 2015.

No other primes through a(10000). - Robert Price, Nov 04 2018

Links

Table of n, a(n) for n=1..19.

Mathematica

Module[{nn=30, c}, c=Drop[Range[nn], {12}]; Table[FromDigits[Flatten[IntegerDigits/@Take[c, n]]], {n, nn - 1}]] (* Vincenzo Librandi, Nov 05 2018 *)

Crossrefs

Cf. A007908, A262299, A262300, A262571-A262582.

See A262300 for more about this problem.

Sequence in context: A060555 A138957 A007908 * A262581 A262580 A262579

Adjacent sequences: A262579 A262580 A262581 * A262583 A262584 A262585

Keyword

nonn,base

Author

N. J. A. Sloane, Sep 25 2015

Status

approved