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21 Blocks

Math brain teasers require computations to solve.

 Puzzle ID: #16578 Fun: (2.23) Difficulty: (2.08) Category: Math Submitted By: Drakar

One day, Drakar was studying for an algebra test when he noticed that his younger sibling made a pyramid of 21 blocks. Each row, from the bottom up, had one less block than the lower one.

"Hmm, I wonder how many different pyramids I can make. Now, I can only switch the blocks with other blocks on the row. So blocks in the fourth row can only be switched with other blocks from the fourth row. And I can switch blocks from as many rows I like, and count it as one different pyramid."

After thinking for a minute he took out a calculator and quickly figured out the answer. How many different pyramids can be made?

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