Thanks for the response, guys! The mickey mouse integrated chainring it came with, according to Dahon, and my count, is only 38T, even though they listed the gearing you quoted, Bruce.
I'm certainly not a super strong rider, but I'm in NYC, which is mostly flat, except when going over the bridges to Brooklyn. I almost exclusively use 3rd gear on this bike, which is a waste. Sheldon Brown says you save on wear if you stay with even numbers (wonder why?), so based on the info you both gave me I'm going to look for a 14T.
This one should fit (?)
http://www.amazon.com/Sturmey-Archer-14t-coaster-brake-cog/dp/B003RLE95G
Last edited by wesgreen; 11-09-15 at 07:15 PM.