The On-Line Encyclopedia of Integer Sequences (OEIS)

A208595 revision #7

A208595

Number of n-bead necklaces labelled with numbers -6..6 not allowing reversal, with sum zero

1, 7, 43, 371, 3431, 34153, 353333, 3770475, 41165305, 457714497, 5164908167, 58997692301, 680874861687, 7926902673655, 92986983743513, 1097999648804923, 13040634990748733, 155677447454317639, 1866995100779692627, 22482675584863229261

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OFFSET

1,2

LINKS

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

FORMULA

a(n) = (1/n) * Sum_{d | n} totient(n/d) * A201550(d). - Andrew Howroyd, Mar 02 2017

EXAMPLE

Some solutions for n=4

.-4...-5...-4...-6...-5...-3...-4...-1...-4...-6...-6...-4...-6...-1...-5...-4

..4....2...-3....5....0....1....0....0....2...-1....3....2....5...-1....4....2

..0...-1....4....1....0....2...-1....0...-3....1....2...-2...-4....0....2....4

..0....4....3....0....5....0....5....1....5....6....1....4....5....2...-1...-2

CROSSREFS

Column 6 of A208597.

Sequence in context: A193705 A164775 A127999 * A121675 A243273 A377154

Adjacent sequences: A208592 A208593 A208594 * A208596 A208597 A208598

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 29 2012

EXTENSIONS

a(15)-a(20) from Andrew Howroyd, Mar 02 2017

STATUS

approved