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A262579 Concatenation of the numbers from 1 to n but omitting 9. 0
1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 1234567810, 123456781011, 12345678101112, 1234567810111213, 123456781011121314, 12345678101112131415, 1234567810111213141516, 123456781011121314151617, 12345678101112131415161718, 1234567810111213141516171819, 123456781011121314151617181920 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 3 12:37 EDT 2020. Contains 333197 sequences. (Running on oeis4.)