OFFSET
1,6
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
Sum mu(d)*A056286(n/d) where d|n.
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, 6-j)*binomial(6, j)*(-1)^j, j=0..6):
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, 6 - j]*Binomial[6, j]*(-1)^j, {j, 0, 6}];
Table[a[n], {n, 1, 30}] (* Jean-François Alcover, Jun 06 2018, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved