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 A306738 #6 Mar 06 2019 16:38:36 %S A306738 1,1,1,2,2,13,20,144,264,2783,6208,79118,204448,3182225,9411840, %T A306738 170576156,566725760,11804363619,43573050368,1023207993178, %U A306738 4152609019392,108681408827381,481065936784384,13880706183899752 %N A306738 Number of permutations of [n] allowing i->i+j (mod n), j=0..ceiling(n/2)-1. %F A306738 a(n) = A008305(n,ceiling(n/2)). %Y A306738 Cf. A008305. %K A306738 nonn %O A306738 0,4 %A A306738 _Alois P. Heinz_, Mar 06 2019