%I #3 May 10 2013 12:45:03
%S 1,11,101,1111,10001,111111,1010101,11011011,101000101,1111111111,
%T 10001010001,111111111111,1010100010101,11010011001011,
%U 101010101010101,1111111111111111,10001010001010001,111111111111111111
%N Sum_{k=1..n, gcd(n,k) = 1} 10^(k-1).
%C A054431 is concatenation of a(n).
%Y Cf. A054431, A054432.
%K nonn
%O 2,2
%A _Vladeta Jovovic_, Aug 15 2002