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A153038
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Denominators of the fixed point a=(a_1,a_2,...) of the transformation x'= fix(x) where fix(x)_n = Sum_{d|n} d x_d, i.e., fix(a)=a.
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4
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1, -1, -2, 3, -4, 2, -6, -21, 16, 4, -10, -6, -12, 6, 8, 315, -16, -16, -18, -12, 12, 10, -22, 42, 96, 12, -416, -18, -28, -8, -30, -9765, 20, 16, 24, 48, -36, 18, 24, 84, -40, -12, -42, -30, -64, 22, -46, -630, 288, -96, 32, -36, -52, 416, 40, 126, 36, 28, -58, 24, -60, 30, -96, 615195, 48, -20, -66, -48, 44, -24, -70, -336, -72, 36
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OFFSET
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1,3
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COMMENTS
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The absolute values are Pazderski's multiplicative psi(n). - R. J. Mathar, Apr 03 2012
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LINKS
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FORMULA
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For n with prime factorization n = p_1^{r_1}*...*p_s^{r_s} the n-th term is a(n) = Product_{k=1..s} Product_{j=1..r_k} (1 - p_k^j).
G.f.: The Dirichlet series for 1/a(n) is Product_{j>= 1} 1/zeta(s+j) = Product_{p prime} Product_{j>= 1} (1 - 1/p^(s+j)) where zeta(s) is Riemann's zeta function.
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MAPLE
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local f, a, p, e;
if n = 1 then
1;
else
a := 1 ;
for f in ifactors(n)[2] do
p := op(1, f) ;
e := op(2, f) ;
a := a*mul(1-p^s, s=1..e) ;
end do:
return a ;
end if;
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MATHEMATICA
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a[1] = 1; a[n_] := (x = 1; Do[p = f[[1]]; e = f[[2]]; x = x*Product[1 - p^s, {s, 1, e}], {f, FactorInteger[n]}]; x); Table[a[n], {n, 1, 46}] (* Jean-François Alcover, May 15 2012, after R. J. Mathar *)
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PROG
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(PARI) a(n)=my(f=factor(n)); prod(k=1, #f[, 1], prod(j=1, f[k, 2], 1-f[k, 1]^j)) \\ Charles R Greathouse IV, Sep 18 2012
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CROSSREFS
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KEYWORD
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easy,eigen,frac,mult,sign
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AUTHOR
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Natascha Neumaerker (naneumae(AT)math.uni-bielefeld.de), Dec 17 2008
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EXTENSIONS
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STATUS
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approved
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