I remember past references to the Wolfram problem generator but this is a separate and free resource:

http://mathworld.wolfram.com/

I think it is a great resource for mathy kids (or their forgetful parents). DS couldn't solve a particular factorial sequence that was an application of the Perrin Sequence and this site had a decent reference page regarding the sequence.

What does "solve a particular factorial sequence" mean?

Quantum2003 - thank you. A good site, an encyclopedia packed with math topics, good site navigation and cross-references, and references to textbooks.

E. g., http://mathworld.wolfram.com/HeronianTriangle.html .

Solving a sequence means determining the pattern of the sequence. You analyze the first few terms of a sequence to determine the subsequent terms of the sequence. In this case, DS was presented with {3! 0! 2! 3! 2! 5!. . . } Without my help he couldn't deduce the subsequent terms, which were 5! 7! 10! . . .

You're welcome. I often find excellent resources on this forum so wanted to share what was helpful to us.