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 A155745 #1 Feb 27 2009 03:00:00
%S A155745 1,1,2,3,7,21,143
%N A155745 a(n) = number of distinct (n+1)- nonnegative integer vectors describing, up to symmetry, the hyperplanes of the real n-dimensional cube.
%C A155745 Related to the sequence a'(n): 1,1,2,3,7,21,131. The sequence a'(n) has a recursive definition.
%C A155745 The following holds: a(n)>a'(n) for n>6.
%D A155745 Ilda P. F. da Silva, Recursivity and geometry of the hypercube, Linear Algebra and its Apllications, 397(2005),223-233
%e A155745 For n=3 a(3)=2 because the 2 vectors (0,0,1,1) and (1,1,1,1) describe all the real planes spanned by the points of {-1,1}^3.
%Y A155745 Cf. A007847
%K A155745 hard,nonn
%O A155745 1,3
%A A155745 Ilda P. F. da Silva (isilva(AT)cii.fc.ul.pt), Jan 26 2009