The shift + 3 combination on my keyboard layout (Irish English, en_IE) by default gives the British currency symbol (£). Unfortunately there's no easy combination to give a hashtag as far as I can tell.
What's the easiest way of remapping the Sterling symbol to give a hashtag?
take backup of the file
/usr/share/X11/xkb/symbols/ie
Open the file
/usr/share/X11/xkb/symbols/ie
with geditedit the line like below
Save the file, Close and refresh the shell Alt+F2 r enter