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A351159 Number of polyominoes of n cells with both diagonal symmetries, for which the 180-degree rotational symmetry has an axis that coincides with the center of a square, but without 90-degree rotational symmetry. 2
0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 2, 1, 3, 1, 6, 4, 9, 6, 20, 19, 32, 25, 64, 82, 114, 107, 217, 332, 397, 442, 751, 1316 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,11

COMMENTS

This sequence enumerates a subset of the polyominoes enumerated by A056878.

LINKS

Table of n, a(n) for n=1..32.

FORMULA

For odd n, a(n) = A056878(n); for even n, a(n) = A056878(n) - A351160(n/2).

EXAMPLE

For a(7)=1, the heptomino with exactly fourfold symmetry and axes of symmetry parallel to the diagonals of the cells is composed of two 2 X 2 squares with one cell in common.

CROSSREFS

Cf. A000105, A056878, A351160.

Sequence in context: A205858 A340793 A053222 * A318762 A262598 A191854

Adjacent sequences: A351156 A351157 A351158 * A351160 A351161 A351162

KEYWORD

nonn,more

AUTHOR

John Mason, Feb 03 2022

STATUS

approved

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Last modified February 6 23:12 EST 2023. Contains 360111 sequences. (Running on oeis4.)