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 A297629 #3 Jan 02 2018 11:24:11
%S A297629 0,1,2,5,20,137,1478,22925,481448,13138193,451749962,19104365333,
%T A297629 974417603132,58981977530777,4179837144348686,342799255549127837,
%U A297629 32212592211380729168,3438255899105307857441,413670348773363088131474,55722273751954119897519653,8352810415786907670280952420
%N A297629 a(n) = A297628(n,1).
%o A297629 (Julia)
%o A297629 function A297629List(len::Int)
%o A297629 R = Array{BigInt}(len)
%o A297629 A = fill(BigInt(0), len+1); A[1] = 1
%o A297629 for n in 1:len
%o A297629 for k in n:-1:2 A[k] += A[k+1] end
%o A297629 for k in 2: 1:n A[k] += A[k-1] end
%o A297629 R[n] = A[2]
%o A297629 end
%o A297629 return R
%o A297629 end
%o A297629 println(A297629List(20))
%Y A297629 Cf. A297628.
%K A297629 nonn
%O A297629 0,3
%A A297629 _Peter Luschny_, Jan 02 2018