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Also try math.SE: http://math.stackexchange.com/search?q=recreationalhttps://math.stackexchange.com/search?q=recreational (Perhaps more recreational material appears there than here.)
Also try math.SE: http://math.stackexchange.com/search?q=recreational (Perhaps more recreational material appears there than here.)
Also try math.SE: https://math.stackexchange.com/search?q=recreational (Perhaps more recreational material appears there than here.)