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 A247418 a(n) = Sum_{i=1..n} mu(i)*(-1)^(i+1). 1
 1, 2, 1, 1, 0, -1, -2, -2, -2, -3, -4, -4, -5, -6, -5, -5, -6, -6, -7, -7, -6, -7, -8, -8, -8, -9, -9, -9, -10, -9, -10, -10, -9, -10, -9, -9, -10, -11, -10, -10, -11, -10, -11, -11, -11, -12, -13, -13, -13, -13, -12, -12, -13, -13, -12, -12, -11, -12, -13 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Alternating sums of mu(n), the Moebius function (A008683), from 1 to n. LINKS FORMULA a(n) = Sum_{i=1..n} A008683(i)*(-1)^(i+1). EXAMPLE a(n) = mu(1) - mu(2) + mu(3) - mu(4) + ... + (-1)^(n+1) * mu(n). MAPLE with(numtheory): A247418:=n->add(mobius(i)*(-1)^(i+1), i=1..n): seq(A247418(n), n=1..50); MATHEMATICA Table[Sum[MoebiusMu[i] (-1)^(i + 1), {i, n}], {n, 50}] Accumulate[Table[MoebiusMu[n](-1)^(n+1), {n, 60}]] (* Harvey P. Dale, Oct 19 2018 *) PROG (PARI) a(n) = sum(i=1, n, moebius(i)*(-1)^(i+1)); \\ Michel Marcus, Sep 18 2014 CROSSREFS Cf. A008683 (moebius function). Cf. A068773 (alternating sums of eulerphi(n)). Cf. A068762 (alternating sums of sigma(n)). Sequence in context: A281871 A131334 A004602 * A229899 A153764 A294509 Adjacent sequences:  A247415 A247416 A247417 * A247419 A247420 A247421 KEYWORD sign,easy AUTHOR Wesley Ivan Hurt, Sep 16 2014 STATUS approved

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Last modified October 19 13:01 EDT 2019. Contains 328222 sequences. (Running on oeis4.)