cp's OEIS Frontend

A208667 Number of 2n-bead necklaces labeled with numbers 1..4 allowing reversal, with neighbors differing by exactly 1.

%I A208667 #11 Mar 20 2017 09:50:13
%S A208667 3,5,8,14,24,47,89,187,396,881,1990,4645,10935,26211,63320,154378,
%T A208667 378444,933023,2308957,5735372,14286908,35683815,89324138,224057919,
%U A208667 563033979,1417210457,3572641304,9018885122,22796905056,57692673963,146167385345,370710166435
%N A208667 Number of 2n-bead necklaces labeled with numbers 1..4 allowing reversal, with neighbors differing by exactly 1.
%H A208667 Andrew Howroyd, <a href="/A208667/b208667.txt">Table of n, a(n) for n = 1..100</a>
%F A208667 a(n) = (2*A208723(n) + A090991(n))/4. - _Andrew Howroyd_, Mar 19 2017
%e A208667 All solutions for n=4:
%e A208667 ..1....2....2....2....1....1....1....1....1....3....1....1....2....2
%e A208667 ..2....3....3....3....2....2....2....2....2....4....2....2....3....3
%e A208667 ..1....2....2....2....1....1....3....3....3....3....3....1....4....4
%e A208667 ..2....3....3....3....2....2....4....2....2....4....2....2....3....3
%e A208667 ..1....4....2....2....3....1....3....1....3....3....3....3....2....4
%e A208667 ..2....3....3....3....4....2....4....2....4....4....2....2....3....3
%e A208667 ..1....4....2....4....3....3....3....3....3....3....3....3....4....4
%e A208667 ..2....3....3....3....2....2....2....2....2....4....2....2....3....3
%Y A208667 Column 4 of A208671.
%K A208667 nonn
%O A208667 1,1
%A A208667 _R. H. Hardin_, Feb 29 2012
%E A208667 a(25)-a(32) from _Andrew Howroyd_, Mar 19 2017