The number of dots in a geometric pattern.

There are triangular numbers {1, 3, 6, 10, 15, 21, ...} shown here

Square numbers {1, 4, 9, 16, 25, ...}

Pentagonal numbers {1, 5, 12, 22, 35, ...} shown below

etc.

There are triangular numbers {1, 3, 6, 10, 15, 21, ...} shown here

Square numbers {1, 4, 9, 16, 25, ...}

Pentagonal numbers {1, 5, 12, 22, 35, ...} shown below

etc.

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