A157235 - OEIS

A157235

Number of primitive inequivalent oblique sublattices of hexagonal (triangular) lattice of index n (equivalence and symmetry of sublattices are determined using only parent lattice symmetries).

0, 0, 0, 0, 0, 1, 0, 0, 1, 2, 1, 2, 1, 3, 2, 2, 2, 5, 2, 4, 3, 5, 3, 4, 4, 6, 5, 6, 4, 10, 4, 6, 6, 8, 6, 10, 5, 9, 7, 8, 6, 14, 6, 10, 10, 11, 7, 12, 8, 14, 10, 12, 8, 17, 10, 12, 11, 14, 9, 20, 9, 15, 14, 14, 12, 22, 10, 16, 14, 22, 11, 20, 11, 18, 18, 18

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OFFSET

1,10

LINKS

Table of n, a(n) for n=1..76.

John S. Rutherford, Sublattice enumeration. IV. Equivalence classes of plane sublattices by parent Patterson symmetry and colour lattice group type, Acta Cryst. (2009). A65, 156-163. [See Table 5.]

FORMULA

a(n) = A003050(n) - (A000086(n)-A154272(n))/2 - A060594(n). - Andrey Zabolotskiy, Mar 19 2021

CROSSREFS

Cf. A003051 (all sublattices), A003050 (all primitive sublattices), A154272 (primitive sublattices fully inheriting the parent lattice symmetry, inlcuding the orientation of the mirrors), A000086 (primitive rotation-symmetric sublattices, counting mirror images as distinct), A060594 (primitive mirror-symmetric sublattices), A145377 (all sublattices inheriting the parent lattice symmetry), A304182.

Sequence in context: A153024 A066921 A076649 * A086289 A077807 A280152

Adjacent sequences: A157232 A157233 A157234 * A157236 A157237 A157238

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 25 2009

EXTENSIONS

New name and a(1)=0 prepended by Andrey Zabolotskiy, May 09 2018

Terms a(31) and beyond from Andrey Zabolotskiy, Mar 19 2021

STATUS

approved