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 A375518 #21 Feb 15 2025 01:58:00
%S A375518 1,2,8,36,1152,240000,9696240000,11752718457744180000,
%T A375518 15347376819435640459450549232576160000,
%U A375518 23554197523775043569951631809272942030408567274885169881327076295276944000
%N A375518 First differences of A375516.
%C A375518 The terms of A375516 are not well-understood. The present sequence was suggested by the fact that, from a certain point on, the terms of A375516 end with the digits 1200. If powers of 2 and 3 are ignored, the terms of the present sequence appear to be perfect squares.
%H A375518 Alois P. Heinz, <a href="/A375518/b375518.txt">Table of n, a(n) for n = 0..12</a>
%p A375518 s:= proc(n) s(n):= `if`(n=0, 0, s(n-1)+1/(n*b(n))) end:
%p A375518 b:= proc(n) b(n):= 1+floor(1/((1-s(n-1))*n)) end:
%p A375518 a:= n-> denom(s(n+1))-denom(s(n)):
%p A375518 seq(a(n), n=0..10); # _Alois P. Heinz_, Oct 19 2024
%t A375518 s[n_] := s[n] = If[n == 0, 0, s[n - 1] + 1/(n*b[n])];
%t A375518 b[n_] := b[n] = 1 + Floor[1/((1 - s[n - 1])*n)];
%t A375518 a[n_] := Denominator[s[n + 1]] - Denominator[s[n]];
%t A375518 Table[a[n], {n, 0, 12}] (* _Jean-François Alcover_, Feb 14 2025, after _Alois P. Heinz_ *)
%Y A375518 Cf. A374663, A374983, A375516, A375517.
%K A375518 nonn
%O A375518 0,2
%A A375518 _N. J. A. Sloane_, Aug 25 2024
%E A375518 a(0)=1 prepended by _Alois P. Heinz_, Oct 19 2024