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 A215656 #11 Feb 18 2017 13:03:44 %S A215656 147,20522387091091,89544370675021535714607142, %T A215656 8801866915656397716021519532258687362772409962179980790374047406788427 %N A215656 Solution R of (2*u)^2 = R^2 - p*S^2, where p is the n-th prime of the form 4k+1. %C A215656 p = A002144(n), u = A215615(p), and S = A215657(n). %C A215656 A215615 is computed from Wendt's circulant determinant A048954. %C A215656 Brown and Chamberland (2012, p. 600) give explicit formulas for u, R, S. %H A215656 Ezra Brown and Marc Chamberland, <a href="http://www.jstor.org/stable/10.4169/amer.math.monthly.119.07.597">Generalizing Gauss's gem</a>, Amer. Math. Monthly, 119 (Aug. 2012), 597-601. %F A215656 a(n) = sqrt(4*u^2 + p*S^2) with S = A215657(n), p = A002144(n), u = A215615(p). %e A215656 2*A215615(5) = 2*11 = 22 and 22^2 = 147^2 - 5*65^2, so a(1) = 147. %Y A215656 Cf. A002144, A048954, A215615, A215657. %K A215656 nonn %O A215656 1,1 %A A215656 _Jonathan Sondow_, Aug 19 2012