A208669 Number of 2n-bead necklaces labeled with numbers 1..6 allowing reversal, with neighbors differing by exactly 1.

5, 9, 16, 32, 65, 152, 360, 937, 2512, 7034, 20124, 58899, 174408, 522453, 1576468, 4787425, 14607763, 44758541, 137607258, 424343533, 1311982883, 4065937220, 12627227963, 39290663343, 122470374536, 382359843141, 1195524220166, 3743191124783

Offset

1,1

Links

Andrew Howroyd, Table of n, a(n) for n = 1..100

Formula

a(n) = (2*A208725(n) + A090995(n))/4.

Example

All solutions for n=3:
..3....5....2....3....3....2....4....4....2....1....1....2....1....3....4....1
..4....6....3....4....4....3....5....5....3....2....2....3....2....4....5....2
..5....5....2....3....3....4....4....4....4....1....3....2....3....5....6....1
..6....6....3....4....4....3....5....5....5....2....4....3....2....4....5....2
..5....5....4....5....3....4....6....4....4....1....3....2....3....5....6....3
..4....6....3....4....4....3....5....5....3....2....2....3....2....4....5....2

Crossrefs

Column 6 of A208671.

Sequence in context: A088495 A352665 A218611 * A062777 A215331 A208725

Adjacent sequences: A208666 A208667 A208668 * A208670 A208671 A208672

Keyword

nonn

Author

R. H. Hardin, Feb 29 2012

Extensions

a(16)-a(28) from Andrew Howroyd, Mar 19 2017

Status

approved