OFFSET
0,1
COMMENTS
Good approximation up to the 9th decimal digit with 22948/41977.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..10000
EXAMPLE
0.546680324466423...
MAPLE
with(numtheory);
P:=proc(i)
local a, f, n, p, pfs;
a:=0;
for n from i by -1 to 1 do
pfs:=ifactors(n)[2];
f:=n*add(op(2, p)/op(1, p), p=pfs);
a:=1/(a+f);
od;
print(evalf(1/a, 1000));
end:
P(10000);
MATHEMATICA
digits = 119; d[0] = d[1] = 0; d[n_] := d[n] = n*Total[Apply[#2/#1 &, FactorInteger[n], {1}]]; f[m_] := f[m] = Fold[d[#2] + 1/#1 &, 1, Range[m] // Reverse] // RealDigits[#, 10, digits] & // First; f[digits]; f[m = 2 digits]; While[f[m] != f[m/2], m = 2 m]; f[m] (* Jean-François Alcover, Feb 21 2014 *)
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Paolo P. Lava, May 05 2011
STATUS
approved