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

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.

Links

Table of n, a(n) for n=1..79.

Crossrefs

Cf. A008683.

Sequence in context: A119664 A257075 A330034 * A108784 A127252 A244513

Adjacent sequences: A010552 A010553 A010554 * A010556 A010557 A010558

Keyword

sign,easy

Author

N. J. A. Sloane

Extensions

Definition changed by N. J. A. Sloane, Jan 15 2019

Status

approved