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 A358361 #25 Feb 16 2025 08:34:04
%S A358361 1,5,8,7,7,0,2,6,4,7,7,2,7,6,6,0,5,0,7,9,7,1,8,0,1,2,6,6,2,8,5,5,5,3,
%T A358361 7,3,2,2,3,5,4,8,6,2,3,2,4,6,7,7,2,1,2,5,2,7,5,1,6,3,2,0,4,7,3,5,6,6,
%U A358361 5,1,0,4,0,4,6,7,1,8,6,9,5,4,9,5,5,2,2
%N A358361 Decimal expansion of the constant Sum_{j>=0} j!!/(2*j)!, where j!! indicates the double factorial of j.
%C A358361 Sum_{j>=0} j!!/(2j)! converges since Sum_{j>=0} j!!/j! converges by A143280 (and it is trivial to note that (2*j)! >= j! for any positive integer j).
%H A358361 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DoubleFactorial.html">Double Factorial</a>.
%F A358361 Equals Sum_{j>=0} A006882(j)/A010050(j).
%F A358361 Equals Sum_{j>=0} 1/(A264152(j)*j!).
%e A358361 1.587702647727...
%t A358361 RealDigits[1 + Sum[(i)!!/(2i)!, {i,1,200}], 10, 105][[1]]
%Y A358361 Cf. A006882, A010050, A143280, A264152.
%K A358361 cons,easy,nonn
%O A358361 1,2
%A A358361 _Marco Ripà_, Nov 12 2022