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 A319323 #10 Oct 27 2018 03:27:36 %S A319323 2,3,6,14,36,94,246,645,1682,4367,11312,29261,75654,195607,505794, %T A319323 1307977,3382628,8748288,22625594,58516858,151343298,391422104, %U A319323 1012341602 %N A319323 a(n) is the number of column convex polyiamonds with n cells. %C A319323 A polyiamond is column convex if the intersection of its interior with any vertical line through the centers of the cells is connected. %H A319323 Adam Gruber, <a href="https://devweb3000.cis.strath.ac.uk/~xpb16190/LatticeAnimals/LatticeAnimals.jar">Java program to count lattice animals</a>. %e A319323 The only septiamonds that are not column convex are four rotations/reflections of a "7" shape. So a(7) = A001420(7) - 4 = 246. %Y A319323 Cf. A001420 (fixed polyiamonds), A238823 (row convex polyiamonds). %K A319323 nonn,more %O A319323 1,1 %A A319323 _David Bevan_, Sep 27 2018