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 A028938 #22 Nov 20 2016 04:00:17 %S A028938 0,3,-14,69,2065,-28888,2616119,-332513754,8280062505,18784454671297, %T A028938 -10663732503571536,8938035295591025771,31636113722016288336230, %U A028938 -41974401721854929811774227,754388827236735824355996347601 %N A028938 Negative of numerator of y-coordinate of (2n)*P where P is generator for rational points on curve y^2 + y = x^3 - x. %H A028938 Seiichi Manyama, <a href="/A028938/b028938.txt">Table of n, a(n) for n = 1..86</a> %H A028938 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 A028938 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 A028938 a(n) = A028942(2n). - _Seiichi Manyama_, Nov 19 2016 %e A028938 4P = (2, -3). %Y A028938 Cf. A028936, A028937, A028939 (denominator), A028942. %K A028938 sign,frac %O A028938 1,2 %A A028938 _N. J. A. Sloane_