OFFSET
1,2
COMMENTS
Dirichlet inverse of A020639.
LINKS
Eric Weisstein's World of Mathematics, Least Prime Factor
MATHEMATICA
a[1] = 1; a[n_] := a[n] = -Sum[(FactorInteger[n/d][[1, 1]]) a[d], {d, Most @ Divisors[n]}]; Table[a[n], {n, 1, 60}]
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Nov 30 2021
STATUS
approved