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 A232090 #24 Dec 23 2024 14:53:43
%S A232090 1,2,6,12,60,20,140,280,2520,2520,27720,27720,360360,360360,72072,
%T A232090 144144,2450448,272272,5173168,5173168,739024,739024,16997552,
%U A232090 16997552,424938800,424938800,11473347600,11473347600,332727080400,332727080400
%N A232090 Minimal possible denominator for a sum of the form 1 +/- 1/2 +/- 1/3 +/- ... +/- 1/n.
%C A232090 Differs from A203811 from a(18)=272272 on, and from A002805 and A231693 from a(15)=72072 on.
%H A232090 Giovanni Resta, <a href="/A232090/b232090.txt">Table of n, a(n) for n = 1..37</a>
%H A232090 F. T. Adams-Watters, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2013-November/011943.html">Re: Reciprocal Recaman</a>, SeqFan list, Nov 17 2013
%t A232090 nMax = 19; d = {0}; Table[d = Flatten[{d + 1/n, d - 1/n}]; Min[Denominator[d]], {n, nMax}] (* _T. D. Noe_, Nov 19 2013 *)
%o A232090 (PARI) for(n=0,19,m=(n+1)!;for(k=0,2^n-1,m=min(denominator(sum(j=2,n+1,(-1)^bittest(k,j-2)/j,1)),m));print1(m","))
%Y A232090 Cf. A061195 (minimal possible positive numerator).
%K A232090 nonn
%O A232090 1,2
%A A232090 _M. F. Hasler_, Nov 18 2013
%E A232090 Terms a(21)-a(30) from _David W. Wilson_, Nov 19 2013