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%I
%S 0,1,10,11,110,111,1110,1111,11110,11111,111110,111111,1111110,
%T 1111111,11111110,11111111,111111110,111111111,1111111110,1111111111,
%U 11111111110,11111111111,111111111110,111111111111,1111111111110
%N Expansion of x(1+10x)/((1-x^2)(1-10x^2)).
%C The expansion of x(1+kx)/((1-x^2)(1-kx^2)) has a(n)=k^((n+1)/2)/(2(sqrt(k)-1))-(-sqrt(k))^(n+1)/(2(sqrt(k)+1))-(-1)^n/2-(k+1)/(2(k-1))
%C First 4 positive members are the divisors of 6 (the first perfect number), written in base 2 (see A135652, A135653, A135654, A135655). - _Omar E. Pol_, May 04 2008
%F a(n)=10^(n/2)(5/9+sqrt(10)/18+(5/9-sqrt(10)/18)(-1)^n)-(-1)^n/2-11/18.
%Y Cf. A075427, A094025, A080610.
%K easy,nonn
%O 0,3
%A _Paul Barry_, Apr 22 2004
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