

A206256


Decimal expansion of Product_{p prime} (1  3/p^2).


5



1, 2, 5, 4, 8, 6, 9, 8, 0, 9, 0, 5, 8, 0, 9, 2, 9, 8, 3, 3, 4, 4, 2, 7, 9, 9, 9, 0, 8, 9, 7, 5, 3, 5, 4, 0, 5, 7, 1, 9, 8, 4, 6, 8, 7, 2, 7, 8, 9, 2, 2, 8, 4, 6, 9, 4, 2, 2, 0, 4, 9, 6, 1, 0, 7, 4, 4, 0, 1, 0, 1, 9, 6, 1, 7, 1, 5, 4, 5, 8, 3, 7, 5, 4, 9, 1, 1, 1, 2, 2, 7, 1, 5, 7, 2, 8, 8, 3, 9, 9, 1, 7, 4, 7, 4, 6
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OFFSET

0,2


COMMENTS

This is the probability that n, n+1, n+2 all are squarefree.


LINKS

Table of n, a(n) for n=0..105.
Leon Mirsky, Note on an asymptotic formula connected with rfree integers, The Quarterly Journal of Mathematics, Vol. os18, No. 1 (1947), pp. 178182.
Leon Mirsky, Arithmetical pattern problems relating to divisibility by rth powers, Proceedings of the London Mathematical Society, Vol. s250, No. 1 (1949), pp. 497508.


EXAMPLE

0.1254869809058...


MAPLE

# See A175640 using efact := 13/p^2.  R. J. Mathar, Mar 22 2012


MATHEMATICA

$MaxExtraPrecision = 500; m = 500; c = LinearRecurrence[{0, 3}, {0, 6}, m]; RealDigits[(1/4) * Exp[NSum[Indexed[c, n]*(PrimeZetaP[n]  1/2^n)/n, {n, 2, m}, NSumTerms > m, WorkingPrecision > m]], 10, 100][[1]] (* Amiram Eldar, Oct 01 2019 *)


CROSSREFS

Cf. A059956, A065474, A007675, A335131.
Sequence in context: A060710 A271853 A146101 * A093052 A081556 A187012
Adjacent sequences: A206253 A206254 A206255 * A206257 A206258 A206259


KEYWORD

nonn,cons


AUTHOR

N. J. A. Sloane, Feb 05 2012, based on a posting by Warren Smith to the Math Fun Mailing List, Feb 04 2012


EXTENSIONS

More terms from Amiram Eldar, Oct 01 2019
More terms from Vaclav Kotesovec, Dec 17 2019


STATUS

approved



