%N Number of ways to express 1 as the sum of distinct unit fractions such that the sum of the denominators is n.
%H Seiichi Manyama, <a href="/A051907/b051907.txt">Table of n, a(n) for n = 1..150</a>
%H <a href="/index/Ed#Egypt">Index entries for sequences related to Egyptian fractions</a>
%e 1 = 1/2+1/4+1/9+1/12+1/18 = 1/2+1/5+1/6+1/12+1/20. The sum of the denominators of each of these is 45, these are the only 2 with sum of denominators = 45, so a(45)=2.
%Y A051882 lists n such that a(n)=0.
%Y Cf. A051908.
%A _Jud McCranie_, Dec 16 1999
%E R. L. Graham showed that a(n)>0 for n>77.