A390999 Number of free polyforms with n cells of two types: unit squares and isosceles right triangles whose short sides have unit length. Cells are joined along sides of equal lengths.

2, 5, 19, 110, 679, 4787, 34769, 260810, 1986798

Offset

1,1

Links

Table of n, a(n) for n=1..9.

Pontus von Brömssen, Illustration for n<=3.

Crossrefs

Cf. A006074, A390142, A390993, A390996, A391000 (one-sided), A391001 (fixed).

Sequence in context: A107882 A328977 A224691 * A192445 A089126 A113346

Adjacent sequences: A390996 A390997 A390998 * A391000 A391001 A391002

Keyword

nonn,more

Author

Pontus von Brömssen, Nov 27 2025

Status

approved