OFFSET
1,3
MATHEMATICA
a[1] = 1; a[n_] := a[n] = Sum[If[GCD[(n - 1)/d, d] == 1, a[d], 0], {d, Divisors[n - 1]}]; Table[a[n], {n, 1, 60}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 06 2020
STATUS
approved