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A133944
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Sum mu(k), where the sum is over the integers k which are the "non-isolated divisors" of n and mu(k) is the Moebius function (mu(k) = A008683(k)). A positive divisor, k, of n is non-isolated if (k-1) or (k+1) also divides n.
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0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, -1, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, -1, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, -1, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, -1, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0, 0, -1, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, -1, 0, -1, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| A133943(n) = -A133944(n), for n >= 2.
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MAPLE
| A133944 := proc(n) local divs, k, i, a ; divs := convert(numtheory[divisors](n), list) ; a := 0 ; for i from 1 to nops(divs) do k := op(i, divs) ; if k-1 in divs or k+1 in divs then a := a+numtheory[mobius](k) ; fi ; od: RETURN(a) ; end: seq(A133944(n), n=1..120) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 21 2007
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CROSSREFS
| Cf. A133943.
Sequence in context: A172051 A093958 A044936 * A094912 A103673 A028862
Adjacent sequences: A133941 A133942 A133943 * A133945 A133946 A133947
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KEYWORD
| sign
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AUTHOR
| Leroy Quet, Sep 30 2007
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 21 2007
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