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%I #8 May 24 2014 20:19:42
%S 1,111,121111,1331121111,146411331121111,161051146411331121111,
%T 1771561161051146411331121111,194871711771561161051146411331121111,
%U 214358881194871711771561161051146411331121111,2357947691214358881194871711771561161051146411331121111
%N a(n) = concatenation of decimal expansions of powers of 11 (in decreasing order).
%C A068704(11) (presently unknown) is either 0, if every term here is composite, or the index of the first prime in the sequence.
%H Alois P. Heinz, <a href="/A242645/b242645.txt">Table of n, a(n) for n = 0..42</a>
%F a(n) is the concatenation of 11^n, 11^(n-1), ..., 121, 11, 1.
%p a:= proc(n) option remember;
%p `if`(n=0, 1, parse(cat(11^n, a(n-1))))
%p end:
%p seq(a(n), n=0..10); # _Alois P. Heinz_, May 24 2014
%Y Cf. A068704, A242646.
%K nonn,base
%O 0,2
%A _N. J. A. Sloane_, May 23 2014