CENTERED PENTAGONAL NUMBER

A 'centered pentagonal number' is a centered figurate number that represents a pentagon with a dot in the center and all other dots surrounding the center in successive pentagonal layers. The centered pentagonal number for ''n'' is given by the formula
$\{\{(5n^2\; +\; 5n\; +\; 2)\}\; over\; 2\}$.
The first few centered pentagonal numbers are
1, 6, 16, 31, 51, 76, 106, 141, 181, 226, 276, 331, 391, 456, 526, 601, 681, 766, 856, 951, 1051, 1156, 1266, 1381, 1501, 1626, 1756, 1891, 2031, 2176, 2326, 2481, 2641, 2806, 2976
The parity of centered pentagonal numbers follows the pattern even-even-odd-odd, and in base 10 one can notice that their ones' digits follow the pattern 6-6-1-1.

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See also

External link

See also

★ Pentagonal number

★ Polygonal number

External link

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