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A157224 Number of primitive inequivalent (up to Pi/2 rotation) non-square sublattices of square lattice of index n. 2
0, 1, 2, 3, 2, 6, 4, 6, 6, 8, 6, 12, 6, 12, 12, 12, 8, 18, 10, 18, 16, 18, 12, 24, 14, 20, 18, 24, 14, 36, 16, 24, 24, 26, 24, 36, 18, 30, 28, 36, 20, 48, 22, 36, 36, 36, 24, 48, 28, 44, 36, 42, 26, 54, 36, 48, 40, 44, 30, 72, 30, 48, 48, 48, 40, 72, 34, 54 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..68.

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 4.]

FORMULA

a(n) = (A001615(n) - A000089(n))/2. - Andrey Zabolotskiy, May 09 2018

CROSSREFS

Cf. A000089 (primitive square sublattices), A002654 (all square sublattices), A145392 (all sublattices), A001615, A304182.

Sequence in context: A329282 A197289 A161888 * A097914 A286633 A286586

Adjacent sequences:  A157221 A157222 A157223 * A157225 A157226 A157227

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 25 2009

EXTENSIONS

New name and more terms from Andrey Zabolotskiy, May 09 2018

STATUS

approved

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Last modified August 8 08:27 EDT 2020. Contains 336293 sequences. (Running on oeis4.)