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%I #16 May 27 2023 06:37:27
%S 1,3,12,52,237,1113,5339,26011,128247,638346,3201967,16164384,82044151
%N Number of 3-dimensional directed animals of size n.
%C Fixed 3-dimensional fixed polycubes with neighborhood vectors [1, 0, 0], [0, 1, 0], and [0, 0, 1].
%C A005773 is the 2-dimensional equivalent: fixed polyominoes with neighborhood vectors [1, 0] and [0, 1].
%C Using neighborhood vectors [+-1, 0, 0], [0, +-1, 0], and [0, 0, +-1] gives A001931.
%Y Cf. A005773.
%K nonn,hard,more
%O 1,2
%A _Joerg Arndt_ and _Márk Péter Légrádi_, May 19 2023
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