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

1,2

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

Links

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

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 *)

Crossrefs

Cf. A007908, A262299, A262571-A262582.

See A262300 for more about this problem.

Sequence in context: A262582 A262581 A262580 * A057932 A262578 A262577

Adjacent sequences: A262576 A262577 A262578 * A262580 A262581 A262582

Keyword

nonn,base

Author

N. J. A. Sloane, Sep 25 2015

Status

approved