SEAMO 2027 - Paper A - SET 10 - Self-study Question 2

Find the sum of the 9th row in the number pyramid below.

1+2+1=4

1+2+3+2+1=9

1+2+3+4+3+2+1=16

1+2+3+4+5+4+3+2+1=25

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Count the first displayed equation as row 1, and continue its increasing-then-decreasing pattern.