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

Author

N. J. A. Sloane, Sep 25 2015

Keywords

• nonn
• base

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

Crossrefs

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

See A262300 for more about this problem.

Programs

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 *)