A sequence is said to be *log-convex* if, for all , .

In this post I give a short, combinatorial-flavored proof that the Bell numbers… 338 more words

A sequence is said to be *log-convex* if, for all , .

In this post I give a short, combinatorial-flavored proof that the Bell numbers… 338 more words

**This is a question that was recently asked on Quora**:

151 more wordsit’s easy to expand

or

or some other but what about aka.

**Q: What is the tenth term of the sequence: 4, 12, 36, 108, …?**

** Answer: 78732**

Explanation: It’s a geometric sequence because each term is multiplied by 3 to get the next term. 62 more words

*Problem:*

Show that

.

*Description:*

In sigma notation, we are trying to prove

. Below, we present the same proof with and without sigma notation. 101 more words