

A137245


Decimal expansion of sum 1/(p * log p) over the primes p = 2, 3, 5, 7, ...


8



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

1,2


COMMENTS

Sum_{p prime} 1/(p^s * log p) equals this value here if s=1, equals A221711 if s=2, 0.22120334039... if s=3. See arXiv:0811.4739.
Erdős (1935) proved that for any sequence where no term divides another, the sum of 1/(x log x) is at most some constant C. He conjectures (1989) that C can be taken to be this constant 1.636..., that is, the primes maximize this sum.  Charles R Greathouse IV, Mar 26 2012
Note that sum 1/(p * log p) is almost (a tiny bit less than) 1 + 2/Pi = 1+A060294 = 1.63661977236758... (Why is it so close?)  Daniel Forgues, Mar 26 2012
Sum 1/(p * log p) is quite close to sum 1/n^2 = Pi^2/6 = 1.644934066... (Cf. David C. Ullrich, "Re: What is Sum(1/p log p)?" for why this is so; mentions A115563.)  Daniel Forgues, Aug 13 2012


REFERENCES

Henri Cohen, Number Theory, Volume II: Analytic and Modern Tools, GTM Vol. 240, Springer, 2007; see pp. 208209.


LINKS

Table of n, a(n) for n=1..87.
Karim Belabas, Henri Cohen, Computation of sum_{p prime} 1/(p^s log(p)), PARI/GP script, 2020.
Henri Cohen, Highprecision computation of HardyLittlewood constants, (1998).
Henri Cohen, Highprecision computation of HardyLittlewood constants. [pdf copy, with permission]
P. Erdős, Note on sequences of integers no one of which is divisible by any other, J. London Math. Soc. 10 (1935), pp. 126128, [DOI].
P. Erdős, Some problems and results on combinatorial number theory, Graph theory and its applications: East and West (Jinan, 1986), Ann. New York Acad. Sci., 576 , pp. 132145, New York Acad. Sci., New York, 1989.
J. K. Lichtman, Almost primes and the BanksMartin conjecture, arXiv:1909.00804 [math.NT], 2019.
R. J. Mathar, Twenty digits of some integrals of the prime zeta function, arXiv:0811.4739 [math.NT], 20082009, table in Section 2.4.
David C. Ullrich, Re: What is Sum(1/p log p)?, posting in newsgroup sci.math.research, 11 Feb 2006.


FORMULA

Equals Sum_(n>=1} 1/(A000040(n)*log A000040(n)).


EXAMPLE

1.63661632335...


PROG

(PARI) See Belabas, Cohen link. Run as SumEulerlog(1) after setting the required precision.


CROSSREFS

Cf. A221711 (p squared), A115563, A319231 (log squared), A319232 (p and log squared).
Sequence in context: A176715 A229522 A227400 * A060294 A181171 A193025
Adjacent sequences: A137242 A137243 A137244 * A137246 A137247 A137248


KEYWORD

cons,nonn


AUTHOR

R. J. Mathar, Mar 09 2008


EXTENSIONS

More terms from Hugo Pfoertner, Feb 01 2020


STATUS

approved



