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 A189283 #24 Nov 08 2022 02:18:08 %S A189283 1,1,2,6,24,114,628,4062,30360,255186,2414292,25350954,292378968, %T A189283 3673917102,49928069188,729534877758,11403682481112,189862332575658, %U A189283 3354017704180052,62654508729565554,1233924707891272728,25550498290562247438 %N A189283 Number of permutations p of 1,2,...,n satisfying p(i+4)-p(i)<>4 for all 1<=i<=n-4. %C A189283 a(n) is also number of ways to place n nonattacking pieces rook + semi-leaper[4,4] on an n X n chessboard. %H A189283 Vaclav Kotesovec, <a href="/A189283/b189283.txt">Table of n, a(n) for n = 0..27</a> (Updated Jan 19 2019) %H A189283 Vaclav Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>, 6ed, 2013, p. 644. %H A189283 Vaclav Kotesovec, <a href="/A189283/a189283.txt">Mathematica program for this sequence</a> %H A189283 George Spahn and Doron Zeilberger, <a href="https://arxiv.org/abs/2211.02550">Counting Permutations Where The Difference Between Entries Located r Places Apart Can never be s (For any given positive integers r and s)</a>, arXiv:2211.02550 [math.CO], 2022. %F A189283 Asymptotics (V. Kotesovec, Mar 2011): a(n)/n! ~ (1 + 7/n + 12/n^2)/e. %Y A189283 Cf. A000255, A189281, A189282, A189255. %K A189283 nonn,hard %O A189283 0,3 %A A189283 _Vaclav Kotesovec_, Apr 19 2011 %E A189283 Terms a(26)-a(27) from _Vaclav Kotesovec_, Apr 20 2012