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A157227
Number of primitive inequivalent (up to Pi/3 rotation) non-hexagonal sublattices of hexagonal (triangular) lattice of index n.
2
0, 1, 1, 2, 2, 4, 2, 4, 4, 6, 4, 8, 4, 8, 8, 8, 6, 12, 6, 12, 10, 12, 8, 16, 10, 14, 12, 16, 10, 24, 10, 16, 16, 18, 16, 24, 12, 20, 18, 24, 14, 32, 14, 24, 24, 24, 16, 32, 18, 30, 24, 28, 18, 36, 24, 32, 26, 30, 20, 48, 20, 32, 32, 32, 28, 48, 22, 36, 32, 48
OFFSET
1,4
FORMULA
a(n) = (A001615(n) - A000086(n))/3. - Andrey Zabolotskiy, May 09 2018
CROSSREFS
Cf. A000086 (primitive hexagonal sublattices), A002324 (all hexagonal sublattices), A145394 (all sublattices), A001615, A304182.
Sequence in context: A033097 A036845 A094269 * A054536 A293664 A001316
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Feb 25 2009
EXTENSIONS
New name and more terms from Andrey Zabolotskiy, May 09 2018
STATUS
approved