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 A189846 #6 Sep 12 2015 11:00:25 %S A189846 1,2,6,24,114,628,4062,30360,251658,2308648,23351268,259031232, %T A189846 3091784268,39697601392,546982720164,8064677125440 %N A189846 Number of ways to place n nonattacking composite pieces rook + semi-rider[4,4] on an n X n chessboard. %C A189846 a(n) is also number of permutations p of 1,2,...,n satisfying p(j+4k)-p(j)<>4k for all j>=1, k>=1, j+4k<=n %C A189846 For information about semi-pieces see semi-bishop (A187235) and semi-queen (A099152). %H A189846 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Number of ways of placing non-attacking queens, kings, bishops and knights</a> (in English and Czech) %H A189846 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189846 Cf. A189283, A099152, A189843, A189844, A189840, A187235 %K A189846 nonn,hard %O A189846 1,2 %A A189846 _Vaclav Kotesovec_, Apr 29 2011