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 A135942 #5 May 21 2018 08:30:33 %S A135942 0,0,0,1,1,8,25,114,438,1826,7339,29876,120346,485155,1947974,7812084, %T A135942 31267765 %N A135942 Number of n-celled polyominoes with perimeter < 2n+2. %C A135942 These are n-cell polyominoes with the perimeter less than the maximum possible one. %C A135942 If we associate a graph to a polyomino with vertices representing cells and edges representing two cells with a common edge, then this sequence enumerates polyominoes whose corresponding graphs have cycles. %F A135942 a(n) = A000105(n) - A131482(n). %K A135942 hard,more,nonn %O A135942 1,6 %A A135942 _Tanya Khovanova_, Mar 03 2008 %E A135942 More terms from _Joerg Arndt_, May 21 2018