A242646 a(n) = concatenation of decimal expansions of powers of 11 (in increasing order).

1, 111, 111121, 1111211331, 111121133114641, 111121133114641161051, 1111211331146411610511771561, 111121133114641161051177156119487171, 111121133114641161051177156119487171214358881, 1111211331146411610511771561194871712143588812357947691, 111121133114641161051177156119487171214358881235794769125937424601

Offset: 0

Author

N. J. A. Sloane, May 23 2014

Keywords

• nonn
• base

Comments

a(2) = 111121 is the first prime in this sequence (compare A242645).

There are no further primes through a(100). - Harvey P. Dale, Sep 12 2014

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..42

Crossrefs

Cf. A242645.

Programs

Maple

a:= proc(n) option remember;
      `if`(n=0, 1, parse(cat(a(n-1), 11^n)))
    end:
seq(a(n), n=0..10);  # Alois P. Heinz, May 24 2014

Mathematica

Module[{nn=15,c},c=IntegerDigits/@(11^Range[0,nn]);Table[FromDigits[ Flatten[ Take[c,n]]],{n,nn+1}]] (* Harvey P. Dale, Sep 12 2014 *)

Formula

a(n) is the concatenation of 1, 11, 121, 11^3, ... 11^(n-1), 11^n.