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 A366859 #5 Nov 12 2023 13:30:25
%S A366859 0,1,3,9,28,95,353,1435,6340,30205,154059,836181,4805816,29125915,
%T A366859 185474289,1237159447,8620179448,62589847993,472554134275,
%U A366859 3702702752513,30057098645316,252375781238167,2188733915100465,19579797280231795,180453411239741852,1711498126672376373
%N A366859 Antidiagonal sums of A366858.
%t A366859 A366858[n_,k_]:=n! SeriesCoefficient[E^((k-1) x)(k Cosh[Sqrt[k]x]+Sqrt[k]Sinh[Sqrt[k]*x])/k,{x,0,n}]; a[n_]:=Sum[A366858[n-k+1,k],{k,n}]; Array[a,26,0] (* or *)
%t A366859 A366858[n_,k_]:=(Sqrt[k]((k+Sqrt[k]-1)^n+(k-Sqrt[k]-1)^n)+(k+Sqrt[k]-1)^n-(k-Sqrt[k]-1)^n)/(2Sqrt[k]); a[n_]:=Sum[A366858[n-k+1,k],{k,n}]; Simplify[Array[a,26,0]]
%Y A366859 Cf. A366858.
%K A366859 nonn
%O A366859 0,3
%A A366859 _Stefano Spezia_, Oct 25 2023