'Heptagonal numbers' definitions:

Definition of 'Heptagonal numbers'

From: GCIDE
  • Heptagonal \Hep*tag"o*nal\, a. [Cf. F. heptagonal.] Having seven angles or sides. [1913 Webster]
  • Heptagonal numbers (Arith.), the numbers of the series 1,
  • 7, 18, 34, 55, etc., being figurate numbers formed by adding successively the terms of the arithmetical series
  • 1, 6, 11, 16, 21, etc. [1913 Webster]