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%I #17 Jun 05 2019 19:39:56
%S 0,0,1,1,2,1,2,1,2,2,1,2,1,3,2,1,3,1,4,2,2,2,0,3,0,1,2,1,4,2,2,2,0,3,
%T 0,1,2,1,4,2,2,3,0,4,0,2,1,1,4,2,3,2,1,5,2,3,1,2,3,2,3,1,3,5,3,4,0,2,
%U 1,3,2,1,5,3,5,2,1,3,2,4,2,1,5,2,6,2,1,5,2,5,2,0,4,0,6,0
%N Number of ways writing n as a sum of two distinct Ulam numbers.
%C After about 10^5 terms, the plot of this sequences begins to show some structure. - _T. D. Noe_, Jan 21 2008
%C When a(n)=1, n is an Ulam number, A002858. A033629 has the terms when a(n)=0. - _Jud McCranie_, Jul 22 2012
%H T. D. Noe, <a href="/A080573/b080573.txt">Table of n, a(n) for n=1..10000</a>
%H T. D. Noe, <a href="http://www.sspectra.com/math/A080573.gif">Plot of 10^5 terms of A080573</a>
%H Rémy Sigrist, <a href="/A080573/a080573.png">Density plot of the first million terms</a>
%H Rémy Sigrist, <a href="/A080573/a080573.txt">C program for A080573</a>
%o (C) See Links section.
%Y Cf. A002858, A033629.
%K easy,nonn
%O 1,5
%A _Naohiro Nomoto_, Feb 22 2003
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