A262579 Concatenation of the numbers from 1 to n but omitting 9.

1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 1234567810, 123456781011, 12345678101112, 1234567810111213, 123456781011121314, 12345678101112131415, 1234567810111213141516, 123456781011121314151617, 12345678101112131415161718, 1234567810111213141516171819, 123456781011121314151617181920

Offset: 1

Author

N. J. A. Sloane, Sep 25 2015

Keywords

• nonn
• base

Comments

There are only two primes among the first 98 terms, namely

1234567810111213141516171819 and 1234567810111213141516171819202122232425262728293031323334353637.

Does this sequence contain any other primes?

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

Crossrefs

Cf. A007908, A262299, A262571-A262582.

See A262300 for more about this problem.

Programs

Mathematica

DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {9}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *)
Module[{nn=20,c},c=Drop[Range[nn],{9}];Table[FromDigits[Flatten[ IntegerDigits/@ Take[c,n]]],{n,nn-1}]] (* Harvey P. Dale, Nov 30 2019 *)