https://wildonblog.wordpress.com/2017/03/20/some-stirling-number-identities-by-differentiation/
Wildon's Weblog 03/20/2017
https://wildonblog.wordpress.com/2017/03/15/regular-abelian-subgroups-of-permutation-groups/
Wildon's Weblog 03/15/2017