Falling and rising factorials - Wikipedia

How many ways are there to climb the eight-step ladder if you always step on either one or two steps at a time? - Quora

Falling and rising factorials - Wikipedia

I had a question on a test, where I was supposed to subtract combinations in forms n choose k (binomial coefficients), the answers were also in forms n choose k, is there

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階乗冪の下降と上昇 - Falling and rising factorials - Wikipedia

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واژه مترادف و متضاد فاکتور با تلفظ فارسی

Combinatorics: A frog can hop either 1 or 3 stairs at a time. In how many ways can he climb to exactly 100 stairs? - Quora

How many ways are there to climb the eight-step ladder if you always step on either one or two steps at a time? - Quora

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Fabling Facebook, Instagram & Twitter on PeekYou

Fabling Facebook, Instagram & Twitter on PeekYou