m,k:
. 1 
m k 
k!m = k
(k-1)!(m-1) 
m,k:. 1 m k (k',m':. k' = k-1 m' = m-1 k!m = kk'!m' )| Rank | Theorem | Name |
| 4 | m,k:. 1 m k k!m = k(k-1)!(m-1) | [factorial_tail_via_iter_step_rw] |
| cites the following: | ||
| 3 | m,k:. 1 m k (k',m':. k' = k-1 m' = m-1 k!m = kk'!m' ) | [factorial_tail_via_iter_step] |