OFFSET
1,2
COMMENTS
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).
LINKS
Eric Weisstein's World of Mathematics, Double Factorial.
EXAMPLE
1.587702647727...
MATHEMATICA
RealDigits[1 + Sum[(i)!!/(2i)!, {i, 1, 200}], 10, 105][[1]]
CROSSREFS
KEYWORD
AUTHOR
Marco Ripà, Nov 12 2022
STATUS
approved