From a posting to the Math Fun mailing list by R. W. Gosper, Dec 03 2009:

(Begin)
Gosper: I just reordered checks.
Bank Lady: Where would you like the numbering to start?
Gosper: What was my last one?
Bank Lady: 1093
Gosper: Well then obviously 3511 .
Bank Lady: [Opens mouth. Decides not to ask. Resumes typing.]
(End)


My question : How many checks can you order for Mr. Gosper's checkbook, using his numbering system?