%I A156870
%S A156870 1,4,18,168,3648,298165
%N A156870 Number of increasing sequences of length 2n with reciprocals adding up 
               to n (1 <= n).
%C A156870 Conjecture: A156869(2n + m, n + m) = a(n) if and only if m >= 0.
%e A156870 For n = 2, the a(2) = 4 sequences are (1, 2, 3, 6), (1, 2, 4, 4), (1, 
               3, 3, 3) and (2, 2, 2, 2) because 1/1 + 1/2 + 1/3 + 1/6 = 1/1 + 1/
               2 + 1/4 + 1/4 = 1/1 + 1/3 + 1/3 + 1/3 = 1/2 + 1/2 + 1/2 + 1/2 = 2.
%Y A156870 a(n) = A156869(2n, n)
%Y A156870 Sequence in context: A059837 A054759 A007153 this_sequence A145075 A058924 
               A154731
%Y A156870 Adjacent sequences: A156867 A156868 A156869 this_sequence A156871 A156872 
               A156873
%K A156870 more,nonn
%O A156870 1,2
%A A156870 Jens Voss (jens(AT)voss-ahrensburg.de), Feb 17 2009
%E A156870 a(6) from M. F. Hasler, Feb 21 2009