OFFSET
1,2
COMMENTS
A polypon is a polyform made up of 30-30-120 triangles from the [3.12^2] Laves tiling, joined along their edges. Because that tiling contains hexagons formed as a union of six triangles, with the division of the hexagon having less symmetry than the hexagon on its own, some polypons can be divided into their constituent triangles in more than one way, and whether the division is significant affects the values of a(n) when n >= 18 is a multiple of 6. For the present sequence, the division into triangles is considered significant. - Joseph Myers, Oct 02 2011
REFERENCES
Computed by Brendan Owen.
LINKS
Andrew Clarke, Other Polyforms
Ed Pegg, Jr., Illustrations of polyforms
Eric Weisstein's World of Mathematics, Polypon [From Eric W. Weisstein, Apr 24 2009]
CROSSREFS
KEYWORD
nonn,nice,hard,more
AUTHOR
N. J. A. Sloane, Nov 04 2000
EXTENSIONS
Link updated by William Rex Marshall, Dec 16 2009
a(21)-a(26) from Joseph Myers, Oct 02 2011
a(27)-a(28) from Sean A. Irvine, Jul 04 2022
STATUS
approved