I found myself in a card game with some friends last night, and pretty early in the game I realized that I was finding “runs” in the cards which simply weren’t playable by normal rules. Most games only recognize runs where the run follows the function ƒ=1n, like 3-4-5. To me, holding 3-6-9 in any suit seems like it should count as a run as well, where ƒ=3n. Other functions would allow somewhat more esoteric runs (2-4-8 counts for ƒ=2n, for example, or a Fibonacci run could include 1-2-3, 2-3-5, 3-5-8, etc.) Maybe a specially-designated “wild” card could be the λ card which would allow one to use functions for runs? Now that would be a card game for geeks.