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A358709
a(n) is the number of free, tree-like polyiamonds, of size 3*n+1, with 120-degree rotational symmetry formed of a central triangle and identical, non-intersecting snakes leading from each of its sides.
1
1, 1, 1, 2, 3, 6, 11, 20, 37, 66, 119, 217, 391, 706, 1274, 2289, 4133, 7435, 13384, 24068
OFFSET
0,4
CROSSREFS
Sequence in context: A010033 A065615 A054182 * A346736 A335628 A355560
KEYWORD
nonn,more
AUTHOR
John Mason, Jan 10 2023
STATUS
approved