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 A078673 #9 Jul 10 2025 16:03:40 %S A078673 1,1,0,2,6,38,247,1831,15287,142199,1459462,16395802,200200031, %T A078673 2640841839,37433428955,567531704959,9165263237530,157084952558930, %U A078673 2847992358978623,54460529906884855,1095499061960126311,23125162555673245847,511150714875199094358 %N A078673 Number of ways of arranging the numbers 1..n in a circle so that there is no consecutive triple i, i+1, i+2 or i, i-1, i-2 (mod n). %C A078673 Arrangement that differ only in the direction in which the cycle is traversed do not count as different. %H A078673 <a href="/index/La#lacings">Index entries for sequences related to shoe lacings</a> %Y A078673 Apart from initial terms, A078628/2. %K A078673 nonn %O A078673 1,4 %A A078673 _N. J. A. Sloane_, Dec 16 2002 %E A078673 More terms from _Sean A. Irvine_, Jul 10 2025