Is the usage of the article "a" correct?

"He is a pedant, sesquipedalianist, and an ambivert" can be rewritten more compactly as "He is a pedant, sesquipedalianist, and ambivert". You should group together items in a list that require the same indefinite article, and only use it once at the start.

Whether you use 'a' or 'an' at the beginning of a list to suit the first item, you do not need to insert the other indefinite article if one of the subsequent items would require it if written or spoken alone. He is an observer, optician, driver, and sculptor.

"Accrue: to come to one as a gain, addition, or increment."

American Heritage Dictionary (1992)
Repeat indefinite articles