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 A348023 #13 Sep 26 2021 02:27:09
%S A348023 1,-1,-5,51,1009,-17765,-636385,15875083,828730833,-26734633497,
%T A348023 -1837389309405,72689703927555,6202163408816881,-290609121018808813,
%U A348023 -29631450442239587305,1604436906627413556075,190333687041180914380065,-11692931012450127257939505,-1582217617564533519968758645
%N A348023 a(n) = [x^n] Product_{k=0..2*n-1} (x + (-1)^k * k).
%H A348023 Seiichi Manyama, <a href="/A348023/b348023.txt">Table of n, a(n) for n = 0..351</a>
%F A348023 a(n) = A047991(2*n-1,n) for n>0.
%o A348023 (PARI) a(n) = polcoef(prod(k=0, 2*n-1, x+(-1)^k*k), n);
%Y A348023 Cf. A047991, A187646, A348024.
%K A348023 sign
%O A348023 0,3
%A A348023 _Seiichi Manyama_, Sep 25 2021