OFFSET
-1,1
COMMENTS
REFERENCES
Steven R. Finch, Mathematical Constants II, Encyclopedia of Mathematics and Its Applications, Cambridge University Press, Cambridge, 2018, p. 244.
LINKS
Jonathan Bayless and Dominic Klyve, Reciprocal sums as a knowledge metric: theory, computation, and perfect numbers, The American Mathematical Monthly, Vol. 120, No. 9 (2013), pp. 822-831, alternative link, preprint.
FORMULA
Equals Sum_{k>=1} 1/A000396(k)^2.
EXAMPLE
0.0290573678948840361775417779770589069661697...
MATHEMATICA
RealDigits[Sum[1/(2^(p - 1)*(2^p - 1))^2, {p, MersennePrimeExponent[Range[14]]}], 10, 100][[1]]
CROSSREFS
KEYWORD
cons,nonn
AUTHOR
Marco Ripà, Dec 26 2020
STATUS
approved