Catalog of programs revealed the emulator you referred to:
1620-13.0.016 (also 160-13.0.018)
141 Data Processing System - An educational Computer for Instruction in
Basic Programming.
On Wed, 15 Jul 2015, Chuck Guzis wrote:
FWIW, Dijkstra disliked the 1620 immensely. I
don't recall his
opinion of the 1401.
There was a somewhat minimal 1401 emulator that could be run on the 1620