A262575 Concatenation of the numbers from 1 to n but omitting 5.

1, 12, 123, 1234, 12346, 123467, 1234678, 12346789, 1234678910, 123467891011, 12346789101112, 1234678910111213, 123467891011121314, 12346789101112131415, 1234678910111213141516, 123467891011121314151617, 12346789101112131415161718, 1234678910111213141516171819, 123467891011121314151617181920

Offset: 1

Author

N. J. A. Sloane, Sep 25 2015

Keywords

• nonn
• base

Comments

The only primes among the first 98 terms are 123467891011 and 123467891011121314151617. See A262552 for further primes in this sequence.

Crossrefs

Cf. A007908, A262299, A262571-A262582.

See A262300 for more about this problem.

For primes see A262552.

Programs

Mathematica

DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {5}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *)
Join[{1,12,123,1234},Table[FromDigits[Flatten[IntegerDigits/@Drop[Range[n],{5}]]],{n,6,20}]] (* Harvey P. Dale, Jan 28 2024 *)