OFFSET
1,2
COMMENTS
See A215474 for the definitions.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..387
EXAMPLE
a(3) = 14 = card{000, 001, 002, 010, 011, 012, 020, 021, 022, 111, 112, 121, 122, 222}.
MATHEMATICA
a[n_] := Sum[1/j Sum[MoebiusMu[j/d] n^d, {d, Divisors[j]}], {j, n}];
Array[a, 20] (* Jean-François Alcover, Jun 27 2019 *)
PROG
(Sage)
def A215475(n):
return add((1/j)*add(moebius(j/d)*n^d for d in divisors(j)) for j in (1..n))
[A215475(n) for n in (1..20)]
(PARI) a(n) = sum(j=1, n, sumdiv(j, d, moebius(j/d)*n^d)/j); \\ Michel Marcus, Jun 27 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Aug 12 2012
STATUS
approved