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 A350623 #18 Jul 08 2022 08:13:05 %S A350623 1,1,1,1,4,9,1,49,121,400,361,7569,36481,38809,1036324,7187761, %T A350623 67092481,34117281,6607901521,68162766400,385083543601,9202249657441, %U A350623 209674135856641,4853089476046161,7099336433764,2600282294202480889,60193393235277536641,1371165544633857017809 %N A350623 a(n) = denominator of the X-coordinate of n*P where P is the generator [0,0] for rational points on the curve y^2 + y = x^3 + x^2. %C A350623 We can take P = P[1] = [x_1, y_1] = [0,0]. Then P[n] = P[1]+P[n-1] = [x_n, y_n] for n >= 2. Sequence gives denominators of the x_n. %D A350623 D. Husemoller, Elliptic Curves, Springer, 1987, p. 28. %D A350623 A. W. Knapp, Elliptic Curves, Princeton, 1992, p. 64. %o A350623 (PARI) See A350622. %Y A350623 Cf. A028940-A028943, A350622-A350625. %K A350623 nonn,frac %O A350623 1,5 %A A350623 _N. J. A. Sloane_, Jan 27 2022