cp's OEIS Frontend

A254079 Number of primitive (=aperiodic) n-bead necklaces with colored beads of exactly 7 different colors.

%I A254079 #6 Jan 25 2015 10:16:56
%S A254079 720,17640,258720,2963520,29317680,263506320,2215825920,17758540440,
%T A254079 137337087888,1033793011440,7621696948320,55289495222640,
%U A254079 396017903136240,2808175618022544,19754629731587280,138087381577881960,960370246763096400,6652267408747194360
%N A254079 Number of primitive (=aperiodic) n-bead necklaces with colored beads of exactly 7 different colors.
%H A254079 Alois P. Heinz, <a href="/A254079/b254079.txt">Table of n, a(n) for n = 7..1000</a>
%p A254079 with(numtheory):
%p A254079 b:= proc(n, k) option remember; `if`(n=0, 1,
%p A254079       add(mobius(n/d)*k^d, d=divisors(n))/n)
%p A254079     end:
%p A254079 a:= n-> add(b(n, 7-j)*binomial(7, j)*(-1)^j, j=0..7):
%p A254079 seq(a(n), n=7..30);
%Y A254079 Column k=7 of A254040.
%K A254079 nonn
%O A254079 7,1
%A A254079 _Alois P. Heinz_, Jan 25 2015