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
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 (sequence A005891 in the OEIS).
The parity of centered pentagonal numbers follows the pattern even-even-odd-odd, and in base 10 the units follow the pattern 6-6-1-1.
See also
External links
This article is issued from Wikipedia - version of the 11/15/2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.