OFFSET
1,5
COMMENTS
Shifts 3 places left when inverse Moebius transform applied twice.
FORMULA
a(1) = a(2) = a(3) = 1; a(n+3) = Sum_{d|n} tau(n/d)*a(d), where tau = number of divisors (A000005).
MATHEMATICA
a[n_] := a[n] = Sum[DivisorSigma[0, (n - 3)/d] a[d], {d, Divisors[n - 3]}]; a[1] = a[2] = a[3] = 1; Table[a[n], {n, 1, 60}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, May 11 2019
STATUS
approved