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 A086823 Coefficient of x^2 in the n-th cyclotomic polynomial. (The same as the coefficient of x^(phi(n)-2) ). 0
 0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, -1, 1, 1, 0, 0, 1, 0, 1, -1, 0, 1, 1, 0, 0, 1, 0, -1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, -1, 0, 1, 1, 0, 0, 0, 0, -1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, -1, 0, 0, 1, 0, 1, 1, 0, -1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, -1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS FORMULA if n is odd a(n) = 1/2 * mu(n)*(mu(n)-1) if n is even a(n) = 1/2 * mu(n)*(mu(n)-1) - mu(n/2). PROG (PARI) a(n) = polcoeff(polcyclo(n), 2); (Wasserman) CROSSREFS Cf. A008683, A000010. Sequence in context: A131735 A131736 A152228 * A104121 A179770 A157928 Adjacent sequences:  A086820 A086821 A086822 * A086824 A086825 A086826 KEYWORD sign AUTHOR Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 07 2003 EXTENSIONS More terms from David Wasserman, Mar 29 2005 STATUS approved

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