OFFSET
1,2
COMMENTS
A pseudo-polytan is a planar figure consisting of n isosceles right triangles joined either edge-to-edge or corner-to-corner, in such a way that the short edges of the triangles coincide with edges of the square lattice. Two figures are considered equivalent if they differ only by a rotation or reflection.
LINKS
Aaron N. Siegel, Illustration showing a(2) = 10. The color of each figure corresponds to its number of symmetries.
EXAMPLE
a(2) = 10, because there are 10 ways of adjoining two isosceles right triangles: 3 distinct edge-to-edge joins (cf. A006074), and 7 distinct corner-to-corner joins.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Aaron N. Siegel, May 24 2022
STATUS
approved