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Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!) 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 (list; graph; refs; listen; history; text; internal format) 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

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Last modified August 18 17:29 EDT 2024. Contains 375269 sequences. (Running on oeis4.)