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 A174285 #47 Nov 06 2022 07:47:07
%S A174285 0,0,0,0,1,3,17,61,235,815,2563,7585,22277,62065,169489,452621,1191617
%N A174285 Number of distinct resistances that can be produced using n equal resistors in series and/or parallel, confined to the five arms (four arms and the diagonal) of a bridge configuration. Since the bridge requires a minimum of five resistors, the first four terms are zero.
%H A174285 Antoni Amengual, <a href="http://dx.doi.org/10.1119/1.19396">The intriguing properties of the equivalent resistances of n equal resistors combined in series and in parallel</a>, American Journal of Physics, 68(2), 175-179 (February 2000). Digital Object Identifier (DOI): 10.1119/1.19396
%H A174285 Sameen Ahmed Khan, <a href="http://arxiv.org/abs/1004.3346/">The bounds of the set of equivalent resistances of n equal resistors combined in series and in parallel</a>, arXiv:1004.3346v1 [physics.gen-ph], (20 April 2010).
%H A174285 Rainer Rosenthal, <a href="/A174285/a174285.txt">Maple programs SetA174285 and SetA174286</a>
%H A174285 Marx Stampfli, <a href="https://dx.doi.org/10.1016%2Fj.amc.2016.12.030">Bridged graphs, circuits and Fibonacci numbers</a>, Applied Mathematics and Computation, Volume 302, 1 June 2017, Pages 68-79.
%H A174285 <a href="/index/Res#resistances">Index to sequences related to resistances</a>.
%e A174285 Five equal unit resistors. Each arm of the bridge has one unit resistor, leading to an equivalent resistance of 1; so the set is {1} and its order is 1.
%e A174285 Six equal unit resistors. Four arms have one unit resistor each and the fifth arm has two unit resistors. Two resistors in the same arm, when combined in series and parallel result in 2 and 1/2 respectively (corresponding to 2: {1/2, 2} in A048211). The set {1/2, 2}, in the diagonal results in {1}. Set {1/2, 2} in any of the four arms results in {11/13, 13/11}. Consequently, with six equal resistors, we have the set {11/13, 1, 13/11}, whose order is 3.
%p A174285 See link section: A174285(n) = nops(SetA174285(n)).
%Y A174285 Cf. A048211, A153588, A174283, A174284, A174286, A176499, A176500, A176501, A176502.
%K A174285 nonn,more
%O A174285 1,6
%A A174285 _Sameen Ahmed Khan_, Mar 15 2010
%E A174285 From Stampfli's paper, a(8) corrected and a(9)-a(12) added by _Eric M. Schmidt_, Sep 09 2017
%E A174285 Name edited by _Eric M. Schmidt_, Sep 09 2017
%E A174285 a(13)-a(17) added by _Rainer Rosenthal_, Feb 04 2021
%E A174285 a(12) corrected by _Marx Stampfli_, Nov 04 2022