login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A192265 Decimal expansion of Sum{k=1..infinity}{1/k^sigma(k)} 2
1, 1, 3, 7, 4, 7, 0, 8, 8, 8, 0, 9, 5, 2, 5, 5, 6, 1, 3, 7, 3, 9, 6, 3, 0, 6, 2, 8, 9, 4, 8, 4, 8, 7, 6, 3, 8, 4, 1, 6, 2, 3, 8, 8, 8, 6, 5, 7, 0, 5, 4, 9, 3, 9, 5, 3, 9, 2, 9, 0, 0, 4, 8, 6, 4, 6, 3, 3, 3, 4, 0, 6, 2, 5, 8, 0, 5, 2, 0, 4, 1, 0, 1, 7, 3, 2 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Rational approximation: 18071/15887. Continued fraction (1,7,3,1,1,1,4,1,2,1,2,3...).

LINKS

Table of n, a(n) for n=1..86.

EXAMPLE

1.137470888095255613739630628948487638416238886570549395392900486463...

MAPLE

with(numtheory);

P:=proc(i)

local a, n;

a:=0;

for n from 1 by 1 to i do a:=a+1/n^sigma(n); od;

print(evalf(a, 300));

end:

P(1000);

MATHEMATICA

Clear[s]; s[n_] := s[n] = RealDigits[ Sum[ 1/k^DivisorSigma[1, k], {k, 1, n}], 10, 86] // First; s[n=100]; While[s[n] != s[n-100], n = n+100]; s[n] (* Jean-Fran├žois Alcover, Feb 13 2013 *)

PROG

(PARI) suminf(k=1, k^-sigma(k)) \\ Charles R Greathouse IV, Jun 29 2011

CROSSREFS

Cf. A192266.

Sequence in context: A193625 A198886 A305202 * A274511 A179706 A231325

Adjacent sequences:  A192262 A192263 A192264 * A192266 A192267 A192268

KEYWORD

nonn,cons

AUTHOR

Paolo P. Lava, Jun 27 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)