Assuming Grover Cleveland is only in there once, the odds of either Adams coming up is 1/44 - since there have been 44 individuals as president. Having the next Adams come up back-to-back would be 1/43 (the remaining pool of candidates after the first Adams is removed). So the odds of them coming up in a row (not just both being in the nine, but actually being in a row) are 1/44 x 1/43, or 1/1,892...quite a feat.
I mean if you have one of them show up, then the odds of the next picture being another one would be 1 in 44. Of course those odds change if you consider it could be before or after the first picture, and also if you consider one might not be on the quiz at all. Anyway, not that unlikely.
Sorry, I should have been more descriptive. I was just ansering Neil's question of "What are the odds of getting two Adams's in a row?". The answer to that specific question is 1 in 1,892. Kal, you are correct about the odds being 1 in 44 for a single event.
I love the idea of the quiz but for some reason the boxes kept going in random order and it took too much time to click on the side and scroll back up only to have the next one jump across or to the bottom. The arrow and tab keys weren't helping. I must have gremlins in my computer.
Glad you like it though!