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A010555
a(n) = 1 if n is the product of an even number of distinct primes, otherwise a(n) = -1.
1
1, -1, -1, -1, -1, 1, -1, -1, -1, 1, -1, -1, -1, 1, 1, -1, -1, -1, -1, -1, 1, 1, -1, -1, -1, 1, -1, -1, -1, -1, -1, -1, 1, 1, 1, -1, -1, 1, 1, -1, -1, -1, -1, -1, -1, 1, -1, -1, -1, -1, 1, -1, -1, -1, 1, -1, 1, 1, -1, -1, -1, 1, -1, -1, 1, -1, -1, -1, 1, -1, -1, -1, -1, 1, -1, -1, 1, -1, -1
OFFSET
1,1
COMMENTS
The old definition was mobius(mobius(n)). The reason for this sequence was that in some ancient version of Maple the command "with(numtheory): A010555 := n->mobius(mobius(n));" worked. But it no longer works, so the definition has been changed.
CROSSREFS
Cf. A008683.
Sequence in context: A119664 A257075 A330034 * A108784 A127252 A244513
KEYWORD
sign,easy
EXTENSIONS
Definition changed by N. J. A. Sloane, Jan 15 2019
STATUS
approved