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 A078603 #14 May 17 2022 11:21:47 %S A078603 1,0,0,0,2,6,46,354,3106,29926,315862,3628906,45132474,604534846, %T A078603 8680957902,133082437730,2169964347282,37505486702678,685046187718022, %U A078603 13186335387855770,266816610979894058,5662225862272325550 %N A078603 Number of ways of arranging the numbers 1..n in a circle so that adjacent numbers do not differ by 1 mod n. %H A078603 <a href="/index/La#lacings">Index entries for sequences related to shoe lacings</a> %F A078603 For n>1, a(n) = 2*A002816(n). %e A078603 a(5) = 2: 1 3 5 2 4, 1 4 2 5 3; a(6) = 6: 1 4 6 2 5 3, 1 5 2 4 6 3, 1 5 3 6 2 4, 1 3 6 4 2 5, 1 4 2 6 3 5, 1 3 5 2 6 4. %Y A078603 Twice A002816. %Y A078603 The sequence n*a(n) is A089222. %Y A078603 See also A078628. %K A078603 nonn %O A078603 1,5 %A A078603 _N. J. A. Sloane_, Dec 11 2002 %E A078603 The sequence was missing a zero; also added a cross-reference _Joel B. Lewis_, Jan 28 2010