Can't remember a whole lot about this. Probably read it directly from the library's science fiction shelf, in the late 80s. A person was somehow being duplicated, I think; each duplication was different. One of the duplicates was an artist; another was an engineer.
The engineer was interrogating a computer, and discovered that the capacity of the computer was given in trits, i.e. triskadecimal units.
I believe he thought to himself how much he would hate learning arithmetic in base 13.
Something about the style now makes me think the author could have been A. E. Van Vogt.
EDIT: the line I thought I remembered actually came from Childhood's End by Arthur C. Clarke:
I'd hate to do arithmetic, George thought to himself, in a system based on fourteen.
This book I'm looking for now definitely did have a base 13 computer, but there was probably no line about learning arithmetic in it.