It was Christmas time when the kid and I started talking about number bases. The air outside was more than normally chill for San Francisco. In the winter here, thanks to the fog, the air’s still damp, so cold feels really cold, but the chill was compensated for by town being even prettier than usual; sporting all it’s holiday lights. People on public transit were more tired than in other seasons; the holiday rush, and December’s early sunsets combined to make a sleepy, almost lethargic atmosphere. The season also seemed to have made our generally friendly fellow bus riders even a little more affable. Smiles swept across their faces a little more quickly. People scooched and shuffled to help each other get into the crowded buses. The kid and I were on one of these buses, returning to the house from who knows where when, mostly just to liven up the ride, and with only the slightest hint of an ulterior motive, I asked her, “How many numbers can you make from a single digit?” Wh