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 A344311 #32 Sep 12 2021 09:58:49 %S A344311 0,0,0,0,5,18,49,96,198,320,550,708,1235,1582,2415,2912,4284,4518, %T A344311 7068,8080,11025,12430,16445,16992,23650,26000,32994,35896,44863, %U A344311 42090,59675,64064,77880,83232,99960,102132,126429,133950,157833,166560,194750,191310,237790,249480,287595,301070 %N A344311 Number of polygons formed outside a regular n-gon when every pair of vertices of the n-gon are joined by an infinite line. %C A344311 See A344857 for other examples and images of the polygons. %C A344311 Only finite polygons are counted. - _N. J. A. Sloane_, Jun 11 2021 %F A344311 For odd n, a(n) = (2*n^4 - 15*n^3 + 34*n^2 - 21*n)/24 (see A344857). %F A344311 a(n) = A344857(n) - A007678(n). %e A344311 a(5) = 5 as the five connected vertices of a regular pentagon form five triangles outside the pentagon, along with sixteen polygons on the inside. %Y A344311 Cf. A344857 (total number of polygons), A007678 (number of polygons inside the n-gon), A345025 (total number of polygons and open regions), A344938, A344857, A344866, A146213 (number of vertices). %K A344311 nonn %O A344311 1,5 %A A344311 _Scott R. Shannon_, Jun 01 2021 %E A344311 Edited by _N. J. A. Sloane_, Sep 12 2021