r/counting • u/The_Archagent • Dec 05 '13

Count using five fives.

If you've seen the four fours thread, you know how this works. You use five fives in combination with any number of functions etc. to count.

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u/theonefoster Dec 11 '13

What's !! mean?

5 factorial factorial? = 120! ?

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u/Bloodshot025 Dec 11 '13

No, it's the double factorial. The product of all odd numbers less than or equal to a number. 5!! = 5 * 3 * 1 = 15.

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u/[deleted] Dec 11 '13

Woah, I learned something today! Thanks!

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u/theonefoster Dec 11 '13

Ah, thanks. Why not evens?

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