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%I #33 Apr 16 2023 09:23:23
%S 0,0,2,7,28,100,368,1335,4912,18125,67477,252573,951363,3601113,
%T 13695150,52291510,200389661,770391542,2970337861,11482318605,
%U 44491635790,172766013959,672185703574,2619993338628
%N 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.
%H John Mason, <a href="/A349329/b349329.txt">Table of n, a(n) for n = 1..50</a>
%F a(n) = A006746(2n) - A349328(2n).
%F a(n) = 2*(A006747(n) + A006748(n)) + A144553(n) + A056878(n) + A006746(n) + 4*A006749(n). - corrected by _John Mason_, Feb 26 2023
%e a(3)=2 because of hexominoes:
%e OO and O
%e O OO
%e O OO
%e OO O
%Y Sequences classifying polyominoes by symmetry group: A000105, A006746, A006747, A006748, A006749, A056877, A056878, A142886, A144553, A144554, A349328.
%K nonn
%O 1,3
%A _John Mason_, Nov 15 2021
%E Name corrected by _John Mason_, Feb 01 2022
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