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7thpentagonalnumber
<-- Enter pentagonal number statement
Calculate pentagonal number 7
The formula for pentagonal number n is as follows
P
n
=
n(3n - 1)
2
Given n = 7, we have:
P
7
=
7(3(7) - 1)
2
P
7
=
7(21 - 1)
2
P
7
=
7(20)
2
P
7
=
140
2
P
7
=
70
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