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 A028939 #28 Nov 19 2016 14:43:47 %S A028939 1,1,1,125,64,24389,2146689,274625,50202571769,4302115807744, %T A028939 1469451780501769,13528653463047586625,343216282443844010111, %U A028939 63061816101171948456692661,495133617181351428873673516736 %N A028939 a(n) = denominator of y-coordinate of (2n)*P where P is the generator for rational points on the curve y^2 + y = x^3 - x. %H A028939 Seiichi Manyama, <a href="/A028939/b028939.txt">Table of n, a(n) for n = 1..86</a> %H A028939 B. Mazur, <a href="https://doi.org/10.1090/S0273-0979-1986-15430-3">Arithmetic on curves</a>, Bull. Amer. Math. Soc. 14 (1986), 207-259; see p. 225. %F A028939 P=(0, 0), 2P=(1, 0); if kP=(a, b) then (k+1)P = (a' = (b^2-a^3)/a^2, b' = -1 - b*a'/a). %F A028939 a(n) = A028943(2n). - _Seiichi Manyama_, Nov 19 2016 %e A028939 8P = (21/25, -69/125). %Y A028939 Cf. A028936, A028937, A028938 (numerator), A028943. %K A028939 nonn,frac %O A028939 1,4 %A A028939 _N. J. A. Sloane_