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a(n) is the number of column convex polyiamonds with n cells.
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%I #10 Oct 27 2018 03:27:36

%S 2,3,6,14,36,94,246,645,1682,4367,11312,29261,75654,195607,505794,

%T 1307977,3382628,8748288,22625594,58516858,151343298,391422104,

%U 1012341602

%N a(n) is the number of column convex polyiamonds with n cells.

%C A polyiamond is column convex if the intersection of its interior with any vertical line through the centers of the cells is connected.

%H Adam Gruber, <a href="https://devweb3000.cis.strath.ac.uk/~xpb16190/LatticeAnimals/LatticeAnimals.jar">Java program to count lattice animals</a>.

%e The only septiamonds that are not column convex are four rotations/reflections of a "7" shape. So a(7) = A001420(7) - 4 = 246.

%Y Cf. A001420 (fixed polyiamonds), A238823 (row convex polyiamonds).

%K nonn,more

%O 1,1

%A _David Bevan_, Sep 27 2018