1-x-2-x-3-x-when-X-is-odd-4-x-when-X-is-evan-5-x-when-X-is-odd-6-x-when-X-is-evan-

Question Number 161234 by mathlove last updated on 14/Dec/21

1 :! x = ?

2 :!! x = ?

3 : x!! = ? w h e n X i s o d d

4 : x!! = ? w h e n X i s e v a n

5 : x!!! = ? w h e n X i s o d d

6 : x!!! = ? w h e n X i s e v a n

Commented by mr W last updated on 14/Dec/21

! x i s d e f i n e d a s n u m b e r o f d e r a n g e m e n t s .

i t h i n k!! x i s n o t d e f i n e d . y o u c o u l d

m e a n! (! x) .

x!! i s d e f i n e d a s x \times (x - 2) \times (x - 4) \times \dots \times k

(k ⩾ 1)

s i m i l a r l y y o u c o u l d d e f i n e x!!! a s

x!!! = x \times (x - 3) \times (x - 6) \times \dots \times k

(k ⩾ 1)

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