OFFSET
1,3
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 1..1000
FORMULA
a = mu * mu * c, where * is Dirichlet convolution and c(n) = 2^(n-1).
EXAMPLE
The a(6) = 24 aperiodic compositions with relatively prime parts are:
(15), (51),
(114), (123), (132), (141), (213), (231), (312), (321), (411),
(1113), (1122), (1131), (1221), (1311), (2112), (2211), (3111),
(11112), (11121), (11211), (12111), (21111).
MATHEMATICA
Table[DivisorSum[n, Function[d, MoebiusMu[n/d]*DivisorSum[d, MoebiusMu[#]*2^(d/#-1)&]]], {n, 20}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 11 2017
STATUS
approved
