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Nonagonal Number

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A Figurate Number of the form $n(7n-5)/2$, also called an Enneagonal Number. The first few are 1, 9, 24, 46, 75, 111, 154, 204, ... (Sloane's A001106).


Sloane, N. J. A. Sequence A001106/M4604 in ``An On-Line Version of the Encyclopedia of Integer Sequences.'' and Sloane, N. J. A. and Plouffe, S. The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.

© 1996-9 Eric W. Weisstein