A056289 Number of primitive (period n) n-bead necklaces with exactly four different colored beads.

0, 0, 0, 6, 48, 260, 1200, 5100, 20720, 81828, 318000, 1222870, 4675440, 17813820, 67769504, 257695800, 980240880, 3731732200, 14222737200, 54278498154, 207438936800, 793940157900, 3043140078000, 11681056021300, 44900438149248, 172824327151140, 666070256468960

Offset

1,4

Comments

Turning over the necklace is not allowed.

References

M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

Links

Alois P. Heinz, Table of n, a(n) for n = 1..1000

Formula

a(n) = Sum_{d|n} mu(d)*A056284(n/d).

Maple

with(numtheory):
b:= proc(n, k) option remember; `if`(n=0, 1,
      add(mobius(n/d)*k^d, d=divisors(n))/n)
    end:
a:= n-> add(b(n, 4-j)*binomial(4, j)*(-1)^j, j=0..4):
seq(a(n), n=1..30);  # Alois P. Heinz, Jan 25 2015

Mathematica

b[n_, k_] := b[n, k] = If[n==0, 1, DivisorSum[n, MoebiusMu[n/#]*k^#&]/n]; a[n_] := Sum[b[n, 4-j]*Binomial[4, j]*(-1)^j, {j, 0, 4}]; Table[a[n], {n, 1, 30}] (* Jean-François Alcover, Feb 20 2017, after Alois P. Heinz *)

Crossrefs

Cf. A027377.

Column k=4 of A254040.

Sequence in context: A353247 A262354 A052771 * A056284 A366622 A293967

Adjacent sequences: A056286 A056287 A056288 * A056290 A056291 A056292

Keyword

nonn

Author

Marks R. Nester

Status

approved