cp's OEIS Frontend

A208720 Number of n-bead necklaces labeled with numbers 1..7 allowing reversal, with no adjacent beads differing by more than 1.

%I A208720 #14 Mar 13 2017 04:23:45
%S A208720 7,13,19,36,58,122,224,502,1066,2528,5902,14717,36557,93987,242387,
%T A208720 635990,1675743,4457771,11903835,31970464,86144382,233001926,
%U A208720 631920076,1718567054,4684178054,12794677456,35012475762,95976563897,263496604025,724445459431
%N A208720 Number of n-bead necklaces labeled with numbers 1..7 allowing reversal, with no adjacent beads differing by more than 1.
%H A208720 Andrew Howroyd, <a href="/A208720/b208720.txt">Table of n, a(n) for n = 1..100</a>
%F A208720 a(2n+1) = (1/2) * (A208776(2n+1) + A002714(n+1)). - _Andrew Howroyd_, Mar 03 2017
%F A208720 a(2n) = (1/2) * A208776(2n) + (1/4) * (A002714(n) + A002714(n+1)). - _Andrew Howroyd_, Mar 03 2017
%e A208720 All solutions for n=3:
%e A208720 ..1....1....6....3....6....5....2....4....4....3....5....4....5....7....6....2
%e A208720 ..2....1....6....4....7....5....3....4....5....3....6....4....5....7....6....2
%e A208720 ..2....1....7....4....7....5....3....5....5....3....6....4....6....7....6....3
%e A208720 ..
%e A208720 ..1....2....3
%e A208720 ..1....2....3
%e A208720 ..2....2....4
%Y A208720 Column 7 of A208721.
%Y A208720 Cf. A208776, A002714.
%K A208720 nonn
%O A208720 1,1
%A A208720 _R. H. Hardin_, Mar 01 2012
%E A208720 a(22)-a(30) from _Andrew Howroyd_, Mar 03 2017