October 1, 2010
Oban is a small town on the west coast of Scotland, home to a rocky port, a small distillery, and a half-built folly started by a banker with not-enough money and less sense. I fondly remember a visit to Oban in 1987. My mother bought a scarf, a tin of shortbread, and a wee dram of the local whiskey at a small shop on the main street (it may have been one of the shops in the picture, I’m not sure) and was scolded by the waitress for using the wrong fork at dinner. Oban numbers have nothing to do with Scotland, except that the name was the occasion of pleasant reminiscing.
MathWorld describes an oban number as a number from which the letter “o” is missing when it is spelled out in words (the letter “o” is “banned”).
Your task is to make a complete list of all the oban numbers. If your language provides a function that spells out a number in words, don’t use it, but write your own instead. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.