HP 50g Double factorial

[FLISZT]

Hello David,


Thank you very much for your insight.

ListExt is installed on my 50G(s), but I'm not very familiar with it.
Following your advice, I did a new and very short program (for n ≥ 0), which weights now 46 bytes instead of 135!

<<
{ 2 − } { 1 > } LWHL
1 + @ To insert the missing 1 in the list.
LPROD
>>

… "et voilà" as (some) English speakers say (sometimes).

0 returns 1
1 returns 1
2 returns 2
3 returns 3
4 returns 8
5 returns 15
…
14 yields 645 120
15 yields 2 027 025
etc.

ListExt, what a great tool!

Best regards