A057724 Number of "polyares" of order n (turning over allowed).

1, 3, 9, 42, 180, 889, 4392, 22432, 115469, 602112, 3161949, 16723643, 88933764, 475286752, 2550780323

Offset

1,2

Comments

An n-are is a shape formed from an n-celled polyomino by removing half of each cell such that edge connections are not broken.

References

Enumeration attributed by Andrew Clarke to Brendan Owen.

Links

Table of n, a(n) for n=1..15.

Andrew Clarke, Polyares

Andrew Clarke, Picture from Andrew Clarke's page showing the 9 polyares of order 3 when turning over is allowed.

Sean A. Irvine, Java program (github)

Eric Weisstein's World of Mathematics, Polyare

Crossrefs

Cf. A057725, A000105.

Sequence in context: A113271 A249045 A183306 * A129879 A264521 A001427

Adjacent sequences: A057721 A057722 A057723 * A057725 A057726 A057727

Keyword

nonn,nice,more

Author

N. J. A. Sloane, Oct 29 2000

Extensions

Link updated by William Rex Marshall, Dec 16 2009

a(9)-a(11) from Sean A. Irvine, Jul 02 2022

Corrected a(8) and added a(12)-a(15) by John Mason, Mar 19 2023

Status

approved