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Observation formula: 1 = 1 square, 1 + 3 = 4 = 2 square, 1 + 3 + 5 = 9 = 3 square This law is expressed by algebraic expression (n is a positive integer) 1 + 3 + 5 + 7 + 9 + ＋（2n－1）＝（ ） emergency
This is an arithmetic sequence
=Square of n
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