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 A347431 #6 Sep 03 2021 12:28:06
%S A347431 1,1,2,7,29,141,832,5729,45217,402359,3985942,43500339,518515997,
%T A347431 6702036193,93361811396,1394334141349,22223762217953,376516856157771,
%U A347431 6756666799667818,128025250352208551,2554170591729180733,53517087513085077221,1174963644698963576488
%N A347431 Antidiagonal sums of A047920.
%H A347431 Alois P. Heinz, <a href="/A347431/b347431.txt">Table of n, a(n) for n = 0..450</a>
%F A347431 a(n) = Sum_{k=0..floor(n/2)} A047920(n-k,k).
%F A347431 a(n) mod 2 = A152822(n).
%p A347431 b:= proc(n, k) option remember;
%p A347431 `if`(k=0, n!, b(n, k-1)-b(n-1, k-1))
%p A347431 end:
%p A347431 a:= n-> add(b(n-k, k), k=0..n/2):
%p A347431 seq(a(n), n=0..23);
%Y A347431 Cf. A047920, A152822.
%K A347431 nonn
%O A347431 0,3
%A A347431 _Alois P. Heinz_, Sep 01 2021