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 A352398 #11 May 16 2022 04:58:04
%S A352398 1,9,45,945,25515,280665,3648645,32837805,186080895,31819833045,
%T A352398 286378497405,6586705440315,98800581604725,8002847109982725,
%U A352398 232082566189499025,7194559551874469775,21583678655623409325,7194559551874469775,2395788330774198435075,21562094976967785915675
%N A352398 Denominators of partial sums of the Madhava series for Pi/(2*sqrt(3)) = A093766.
%C A352398 For a comment and references see A352397.
%F A352398 a(n) = denominator(Sum_{j=0..n} (-1)^j/((2*j+1)*3^j)), for n >= 0.
%t A352398 Denominator @ Accumulate @ Table[(-1)^j/((2*j + 1)*3^j), {j, 0, 20}] (* _Amiram Eldar_, Apr 08 2022 *)
%o A352398 (PARI) a(n) = denominator(sum(j=0, n, (-1)^j/((2*j+1)*3^j))); \\ _Michel Marcus_, Apr 08 2022
%Y A352398 Cf. A352397 (numerators).
%Y A352398 Cf. A093766.
%K A352398 nonn,frac,easy
%O A352398 0,2
%A A352398 _Wolfdieter Lang_, Apr 07 2022