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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)/ 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 evenevenoddodd, and in base 10 one can notice that their ones' digits follow the pattern 6611. See also * Pentagonal number * Polygonal number * Centered polygonal number Links * Eric W. Weisstein, Centered pentagonal number at MathWorld. Retrieved from "http://en.wikipedia.org/" 
