For example the word "hello" has the letter "l" appearing twice in a row. Are there any letters that never appear twice in a row?
Edit for clarification: I'm asking whether or not every letter in the english alphabet appears next to itself in some word.
Examples:
A - Aardvark
B - Babbling
C - Eccentric
D - Forbidden
E - Keen
F - Buff
G - Bugged
H - ??
I - Hawaii
J - ?? etc.
Is there a website or anything that would have a list like this?