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A349329
Number of polyominoes with 2n cells and exactly one line of reflection symmetry, where that one line is parallel to the grid and passes through the corner of at least one square.
4
0, 0, 2, 7, 28, 100, 368, 1335, 4912, 18125, 67477, 252573, 951363, 3601113, 13695150, 52291510, 200389661, 770391542, 2970337861, 11482318605, 44491635790, 172766013959, 672185703574, 2619993338628
OFFSET
1,3
LINKS
FORMULA
a(n) = A006746(2n) - A349328(2n).
a(n) = 2*(A006747(n) + A006748(n)) + A144553(n) + A056878(n) + A006746(n) + 4*A006749(n). - corrected by John Mason, Feb 26 2023
EXAMPLE
a(3)=2 because of hexominoes:
OO and O
O OO
O OO
OO O
CROSSREFS
Sequences classifying polyominoes by symmetry group: A000105, A006746, A006747, A006748, A006749, A056877, A056878, A142886, A144553, A144554, A349328.
Sequence in context: A123363 A102961 A155581 * A048504 A092465 A099488
KEYWORD
nonn
AUTHOR
John Mason, Nov 15 2021
EXTENSIONS
Name corrected by John Mason, Feb 01 2022
STATUS
approved