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 A349783 #19 Dec 10 2021 18:53:06
%S A349783 1,1,17,619,38009,3555161,475971957,87025015687,20913570481057,
%T A349783 6401730410889889,2432850898346888777,1123996170986262914979,
%U A349783 620447951124750866054313,403291412174732586716167529,304888338816008019564815376029,265252859069372498997243448483215
%N A349783 a(n) = Sum_{j=0..n} |Stirling1(2*n, j)|.
%F A349783 a(n) = Sum_{j=0..n} A132393(2n,j). - _Alois P. Heinz_, Dec 10 2021
%p A349783 b:= proc(n, k) option remember; `if`(n=0, 1, `if`(k=0, 0,
%p A349783 add(b(n-j, k-1)*binomial(n-1, j-1)*(j-1)!, j=1..n)))
%p A349783 end:
%p A349783 a:= n-> b(2*n, n):
%p A349783 seq(a(n), n=0..15); # _Alois P. Heinz_, Dec 09 2021
%t A349783 a[n_] := Sum[Abs[StirlingS1[2*n, j]], {j, 0, n}]; Array[a, 16, 0] (* _Amiram Eldar_, Dec 09 2021 *)
%o A349783 (PARI) a(n) = sum(j=0, n, abs(stirling(2*n, j, 1))); \\ _Michel Marcus_, Dec 09 2021
%o A349783 (Python)
%o A349783 from sympy.functions.combinatorial.numbers import stirling
%o A349783 def A349783(n): return sum(abs(stirling(2*n,j,kind=1)) for j in range(n+1)) # _Chai Wah Wu_, Dec 09 2021
%Y A349783 Central terms of A349782.
%Y A349783 Cf. A132393.
%K A349783 nonn
%O A349783 0,3
%A A349783 _Peter Luschny_, Dec 09 2021