%I #20 Aug 14 2018 01:04:34
%S 1,5,47,733,15907,443825,15129599,609432421,28322451979,1491650309705,
%T 87799033276583,5711697248522077,406948643125302163,
%U 31515118552199419745,2635823964117955940111,236779241276954626064149,22736883802469421935493211
%N Number of inequivalent expressions involving n operands, ignoring sign.
%C Similar to A140606, but for example, (a-b)/(c-d) and (b-a)/(c-d) are also regarded as the same.
%H Muniru A Asiru, <a href="/A247982/b247982.txt">Table of n, a(n) for n = 1..100</a>
%H Azuma Seiichi, <a href="http://searial.web.fc2.com/math/sisoku.html">Expressions with n variables</a>
%F a(n) = A182173(n)/2. - _Zhujun Zhang_, Aug 11 2018
%Y Cf. A140606, A182173.
%K nonn,more
%O 1,2
%A _Azuma Seiichi_, Sep 28 2014
%E a(7)-a(17) from _Muniru A Asiru_, Aug 13 2018