

A182170


Decimal expansion of constant C = maximum value of 2*sum(i=1..n, prime(i))/(n^2*log(n)).


0



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

1,3


COMMENTS

According to Bach and Shallit (1996), sum(i=1..n, Prime(i)) ~ n^2*log(n)/2. Consequently, the function 2*sum(i=1..n, Prime(i))/(n^2*log(n)) tends to 1 as n tends to infinity, however it has a maximum value of 1.0820514... when n=341276. In precise terms this constant is 802812394173*2/(341276^2*log(341276)) and it provides an upper bound for sum(i=1..n, prime(n)) <= (802812394173*2/(341276^2*log(341276)))*n^2*Log(n)/2 for all n>=15. The prime sums tables of R. J. Mathar, A007504 show that a maximum for C occurs between n=200000 and n=400000. Further refinement gives the maximum value of C at n=341276 where the sum of primes from 2 through to 4889407, inclusively, gives 802812394173.


REFERENCES

E. Bach and J. Shallit, Section 2.7 in Algorithmic Number Theory, Vol. 1: Efficient Algorithms, Cambridge, MIT Press, 1996.


LINKS

Table of n, a(n) for n=1..83.
Eric W. Weinstein, MathWorld: Prime Sums


FORMULA

C = 802812394173*2/(341276^2*log(341276)).


EXAMPLE

1.0820514451923950650336815288978985575393063847...


MATHEMATICA

table=Table[2Sum[Prime[i], {i, 1, n}]/(n^2Log[n]), {n, 341200, 341400}]; max=Max[table]; n=1; While[table[[n]]!=max, n++]; Print[N[max, 100], " at n = ", n1+341200]


PROG

(PARI) 1605624788346/(341276^2*log(341276)) \\ Charles R Greathouse IV, Apr 16 2012


CROSSREFS

Cf. A007504.
Sequence in context: A021850 A197576 A277313 * A011105 A098829 A190404
Adjacent sequences: A182167 A182168 A182169 * A182171 A182172 A182173


KEYWORD

nonn,cons


AUTHOR

Frank M Jackson, Apr 16 2012


STATUS

approved



