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A020513
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Cyclotomic polynomials evaluated at x=-1.
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9
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-1, -2, 0, 1, 2, 1, 3, 1, 2, 1, 5, 1, 1, 1, 7, 1, 2, 1, 3, 1, 1, 1, 11, 1, 1, 1, 13, 1, 1, 1, 1, 1, 2, 1, 17, 1, 1, 1, 19, 1, 1, 1, 1, 1, 1, 1, 23, 1, 1, 1, 5, 1, 1, 1, 3, 1, 1, 1, 29, 1, 1, 1, 31, 1, 2
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OFFSET
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0,2
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LINKS
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FORMULA
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For n >= 3: if n = 2*p^m with a prime p then a(n) = p otherwise a(n) = 1. - Ola Veshta (olaveshta(AT)my-deja.com), Jun 01 2001
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MAPLE
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with(numtheory, cyclotomic); f := n->subs(x=-1, cyclotomic(n, x)); seq(f(i), i=0..64);
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MATHEMATICA
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PROG
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(PARI) a(n) = if (n==0, -1, subst(polcyclo(n), x, -1)); \\ Michel Marcus, Apr 22 2016
(PARI) a(n) = if (n==0, -1, if (n==1, -2, if (n==2, 0, if (!(n % 2) && isprimepower(n/2, &p), p, 1)))); \\ Michel Marcus, Nov 23 2016
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CROSSREFS
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Cf. A138929 (2*p^m, m >= 0 values).
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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