A262581 Concatenation of the numbers from 1 to n but omitting 11.

1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678910, 1234567891012, 123456789101213, 12345678910121314, 1234567891012131415, 123456789101213141516, 12345678910121314151617, 1234567891012131415161718, 123456789101213141516171819, 12345678910121314151617181920

Offset

1,2

Comments

There are only two primes among the first 98 terms, namely 123456789101213 and

1234567891012131415161718192021222324252627282930313233343536\

373839404142434445464748495051525354555657585960616263.

Does this sequence contain any other primes?

No other primes through a(10000). - Robert Price, Nov 05 2018

Links

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

Mathematica

DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {11}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *)

Prog

(PARI) terms(n) = my(s="", i=0); for(k=1, n, if(k!=11, s=concat(s, Str(k)); print1(eval(s), ", "); i++); if(i==n, break))
/* Print initial 20 terms as follows */
terms(20) \\ Felix Fröhlich, Nov 05 2018

Crossrefs

Cf. A007908, A262299, A262571-A262582.

See A262300 for more about this problem.

Sequence in context: A138957 A007908 A262582 * A262580 A262579 A057932

Adjacent sequences: A262578 A262579 A262580 * A262582 A262583 A262584

Keyword

nonn,base

Author

N. J. A. Sloane, Sep 25 2015

Status

approved