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 A174076 #9 Apr 17 2021 08:34:01 %S A174076 1,1,2,6,24,108,632,4408,35336,319056,3205824,35451984,427683560, %T A174076 5588310904,78615281768,1184587864512,19033796498496,324852522308160, %U A174076 5868833343451592,111889157407344424 %N A174076 Number of permutations of length n with no consecutive triples i,i+2,i+4 or i,i-2,i-4. %C A174076 Note for n<5 there are no such subsequences, so those values are trivially n!. Also note it is possible for a permutation to have both i,i+2,i+4 and i,i-2,i-4 triples, as in an example from n=7: (2,4,6,5,3,1,0). This permutation is not counted by a(7). %e A174076 For n=5 there are 5!-a(5)=12 permutations with i,i+2,i+4 or i,i-2,i-4 triples. An examples of one is (4,2,0,1,3). %Y A174076 Cf. A095816, A174077, A174078, A174079. %K A174076 nonn,more %O A174076 0,3 %A A174076 _Isaac Lambert_, Mar 10 2010 %E A174076 a(0)-a(4) and a(10)-a(19) from _Alois P. Heinz_, Apr 14 2021