Theoretically, there are four possible pronunciations of 'vegan' due to two syllables constituting this word, namely, 've'('vee' or 'vay'?) and 'gan'('gun' or 'gen' as in 'generate'?).
The online dictionary merriam-webster.com provides several pronunciations of 'vegan' but as you can see that there are several comments about it at the bottom.
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