Front | Back |
1, 3, 5, 7, ....., ..... .
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1, 3, 5, 7, 9, 11.
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1, 4, 7, 10, ..... , ..... .
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1, 4, 7, 10, 13, 16 .
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1, 2, 4, 7, ..... , ..... .
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1, 2, 4, 7, 11, 16 .
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1, 4, 9, 16, ..... , ..... .
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1, 4, 9, 16, 25 , 36 .
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Write down the number of triangle in the fourth diagram 1, 5, 13, ..... |
1, 5, 13, 21.
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