Using numpad in Vi (Vim) via PuTTY

The answer is in Numpad in PuTTY while using vi [Cialug]:

In the configuration, go to Terminal->Features and check "Disable application keypad mode". Save the settings and enjoy a numeric pad that works!

And for Mac, the answer is in a comment by HaPsantran on this same page and there is a similar answer by nfechner with German screenshots in this answer.

For Mac, go to your Terminal application. Select Preferences, Profiles, Advanced and deselect Allow VT100 application keypad mode.

If using SSH through a terminal you can just go to

Edit -> Num Lock (third from bottom)

It needs to have a checkmark to the left of it.

I have always used this set of mappings to interpret the escape sequences as numbers when $TERM=xterm

imap <Esc>Oq 1
imap <Esc>Or 2
imap <Esc>Os 3
imap <Esc>Ot 4
imap <Esc>Ou 5
imap <Esc>Ov 6
imap <Esc>Ow 7
imap <Esc>Ox 8
imap <Esc>Oy 9
imap <Esc>Op 0
imap <Esc>On .
imap <Esc>OR *
imap <Esc>OQ /
imap <Esc>Ol +
imap <Esc>OS -

I think this was my original source.