Q: What number comes next in the following series: 2, 4, 6, 9, 11, 15, 20, 40, 51*, 55*, 60 and 90?See, I thought I had the answer to this, but if so, there are a couple numbers missing.
*Update: The consensus seems to be that Henry Hook and Will Shortz overlooked a couple terms in the sequence and it should be 2, 4, 6, 9, 11, 15, 20, 40, 51, 55, 60 and 90. Hopefully everyone is able to solve it now with the corrected wording. If anyone has direct access to Will's email, perhaps they could ask for a similar correction to the puzzle on the NPR website.
Will Shortz has confirmed (see his comment) that he extended Henry Hook's original series (2, 4, 6, 9, 11, 15, 20) and in the process overlooked the numbers above. The NPR website has been updated as well. Thanks to everyone that helped clear this up.
Edit: My hint was "See, I..." which sounds like CI which is 101 in Roman numerals
A: 101 is next in the sequence. When represented as Roman numerals, each number in the series requires exactly two letters (II, IV, VI, IX, XI, XV, XX, XL, LI, LV, LX, XC, CI...)