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 A206477 #9 Jul 22 2025 19:28:47
%S A206477 3,3,36,76,690,2996,22368,147472,1284653,11006509
%N A206477 (Number of permutations of {1,2,...,n} for which sums of three consecutive numbers (with wraparound) are all distinct)/2n.
%C A206477 Essentially different ways 1,2,...,n can be placed around a circle so that sums of three consecutive numbers are distinct.
%e A206477 a(4)=3 because up to rotation/reflection the only three permutations which work are 1234, 1243, and 1324
%Y A206477 Cf. A040018
%K A206477 hard,nonn
%O A206477 4,1
%A A206477 _Steve Butler_, Feb 08 2012