This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A304183 #6 May 09 2018 23:02:27 %S A304183 0,0,1,1,2,3,3,4,5,6,5,8,6,9,10,10,8,15,9,14,14,15,11,20,14,18,17,20, %T A304183 14,30,15,22,22,24,22,32,18,27,26,32,20,42,21,32,34,33,23,44,27,42,34, %U A304183 38,26,51,34,44,38,42,29,64,30,45,46,46,40,66,33,50,46 %N A304183 Number of primitive inequivalent oblique sublattices of rectangular lattice of index n. %H A304183 John S. Rutherford, <a href="https://doi.org/10.1107/S010876730804333X">Sublattice enumeration. IV. Equivalence classes of plane sublattices by parent Patterson symmetry and colour lattice group type</a>, Acta Cryst. (2009). A65, 156-163. [See Table 4. Contains errors for n = 24 and 28.] %F A304183 a(n) = (A001615(n) - A304182(n))/2. %Y A304183 Cf. A304182 (primitive mirror-symmetric sublattices), A069734 (all sublattices), A001615 (primitive sublattices of oblique lattice). %K A304183 nonn %O A304183 1,5 %A A304183 _Andrey Zabolotskiy_, May 07 2018