This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A247982 #26 Aug 09 2025 19:37:53 %S A247982 1,5,47,733,15907,443825,15129599,609432421,28322451979,1491650309705, %T A247982 87799033276583,5711697248522077,406948643125302163, %U A247982 31515118552199419745,2635823964117955940111,236779241276954626064149,22736883802469421935493211 %N A247982 Number of inequivalent expressions involving n operands, ignoring sign. %C A247982 Similar to A140606, but for example, (a-b)/(c-d) and (b-a)/(c-d) are also regarded as the same. %H A247982 Muniru A Asiru, <a href="/A247982/b247982.txt">Table of n, a(n) for n = 1..100</a> %H A247982 Seiichi Azuma, <a href="http://searial.web.fc2.com/math/sisoku.html">Expressions with n variables</a> %F A247982 a(n) = A182173(n)/2. - _Zhujun Zhang_, Aug 11 2018 %Y A247982 Cf. A140606, A182173. %K A247982 nonn %O A247982 1,2 %A A247982 _Seiichi Azuma_, Sep 28 2014 %E A247982 a(7)-a(17) from _Muniru A Asiru_, Aug 13 2018