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 A172457 #8 Feb 26 2019 23:03:45
%S A172457 -5,5,-1,1,-1,1,-1,1,-1,25,-25,477481,-477481,49,-49,13082689,
%T A172457 -13082689,1924313689,-1924313689,30489001321,-30489001321,
%U A172457 730192467169,-730192467169,55867983514256281,-55867983514256281,73155570928609
%N A172457 Numerators of first differences of the sequence A172298(n)/A172282(n).
%C A172457 The sequence A172298(n)/A172282(n) = 1, -1/4, 1/36, 0, 1/900, 0, 1/1764, 0, 1/900, 0, 25/4356, ... contains (up to a sign flip of the element at n=1) the squares of the Bernoulli numbers.
%C A172457 The first differences if this sequence of fractions are -5/4, 5/18, -1/36, 1/900, -1/900, 1/1764, -1/1764, 1/900, -1/900, ...
%C A172457 The sequence contains the numerators of these first differences.
%p A172457 Bsq := proc(n)
%p A172457 if n =1 then
%p A172457 -bernoulli(n)^2 ;
%p A172457 else
%p A172457 bernoulli(n)^2 ;
%p A172457 end if;
%p A172457 end proc:
%p A172457 B := [seq(Bsq(n),n=0..30)] ;
%p A172457 read("transforms"); DIFF(B) ;
%p A172457 apply(numer,%) ; # _R. J. Mathar_, Jul 13 2011
%Y A172457 Cf. A172298, A172299.
%K A172457 frac,sign
%O A172457 0,1
%A A172457 _Paul Curtz_, Feb 03 2010