A358361 Decimal expansion of the constant Sum_{j>=0} j!!/(2*j)!, where j!! indicates the double factorial of j.

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, 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, 5, 1, 0, 4, 0, 4, 6, 7, 1, 8, 6, 9, 5, 4, 9, 5, 5, 2, 2

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

Table of n, a(n) for n=1..87.

Eric Weisstein's World of Mathematics, Double Factorial.

Formula

Equals Sum_{j>=0} A006882(j)/A010050(j).

Equals Sum_{j>=0} 1/(A264152(j)*j!).

Example

1.587702647727...

Mathematica

RealDigits[1 + Sum[(i)!!/(2i)!, {i, 1, 200}], 10, 105][[1]]

Crossrefs

Cf. A006882, A010050, A143280, A264152.

Sequence in context: A334482 A243598 A230366 * A197415 A019845 A374171

Adjacent sequences: A358358 A358359 A358360 * A358362 A358363 A358364

Keyword

cons,easy,nonn

Author

Marco Ripà, Nov 12 2022

Status

approved