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 A206478 #9 Jul 22 2025 19:28:53
%S A206478 12,8,76,694,2529,23679,177885,1482021,14666021
%N A206478 (Number of permutations of {1,2,...,n} for which sums of four consecutive numbers (with wraparound) are all distinct)/2n.
%C A206478 Essentially different ways that 1,2,...,n can be placed around a circle so that the sums of three consecutive terms are all distinct.
%e A206478 a(6)=8 because up to rotation/reflection the only three permutations which work are 123465, 123546, 124653, 125364, 126543, 132456, 132645, 136524.
%Y A206478 Cf. A040018
%K A206478 hard,nonn
%O A206478 5,1
%A A206478 _Steve Butler_, Feb 08 2012