

A117536


Nearest integer to locations of increasingly large peaks of abs(zeta(0.5+i*2*pi/log(2)*t)) for increasing real t.


7



0, 1, 2, 3, 4, 5, 7, 10, 12, 19, 22, 27, 31, 41, 53, 72, 99, 118, 130, 152, 171, 217, 224, 270, 342, 422, 441, 494, 742, 764, 935, 954, 1012, 1106, 1178, 1236, 1395, 1448, 1578, 2460, 2684, 3395, 5585, 6079, 7033, 8269, 8539, 11664, 14348, 16808, 28742, 34691
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OFFSET

0,3


COMMENTS

These correspond to increasing peaks of the absolute value of the Riemann zeta function along the critical line. If Z'(s)=0 is a positive zero of the derivative of Z, then Z(s) is the peak value.
The fractional parts of these values are not randomly distributed; r = log(2) * s(n) / (2 pi) shows a very strong tendency to be near an integer.
It would be interesting to have theorems on the distribution of the fractional part of the "r" above, for which the Riemann hypothesis would surely be needed. It would be particularly interesting to know if the absolute value fractional part was constrained to be less than some bound, such as 0.25. This computation could be pushed much farther by someone using a better algorithm, for instance the RiemannSiegel formula and better computing resources. The computations were done using Maple's accurate but very slow zeta function evaluation. They are correct as far as they go, but do not go very far. The terms of the sequence have an interpretation in terms of music theory; the terms which appear in it, 12, 19, 22 and so forth, are equal divisions of the octave which do relatively well approximating intervals given by rational numbers with small numerators and denominators.
This sequence was extended by examining the peaks of zeta(0.5+xi) between each the first million zeros of the zeta function. These record peaks occur between zeros that are relatively far apart. The fractional part of r decreases as the magnitude of r increases.  T. D. Noe, Apr 19 2010


REFERENCES

Edwards, H. M., Riemann's ZetaFunction, Academic Press, 1974
Ramachandra, K., On the MeanValue and OmegaTheorems for the Riemann ZetaFunction, SpringerVerlag, 1995
Titchmarsh, E. C., The Theory of the Riemann ZetaFunction, second revised (HeathBrown) edition, Oxford University Press, 1986


LINKS

Table of n, a(n) for n=0..51.
Andrew Odlyzko, Tables of the zeros of the Riemann zeta function
Wikipedia, Z function
Index entries for zeta function.


EXAMPLE

The function f(m)=zeta(1/2+i*2*pi/log(2)*m) has a local maximum f(m') ~ 3.66 at m' ~ 5.0345, which corresponds to a(5)=round(m)=5. The peak at f(6.035) ~ 2.9 is smaller, and after two more smaller local maxima, there is a larger peak at f(6.9567) ~ 4.167, whence a(6)=7.


PROG

(PARI) {my(c=I/log(2)*2*Pi, f(n)=abs(zeta(.5+n*c)), m=0,
find(x, d, e=1e6)=my(y=f(x)); while(y<(y=f(x+=d))  e<abs(d=d/3), ); x);
for(n=0, 999, if(m<m=max(f(find(n, .01)), m), print1(n", ")))} /* for illustrative purpose only */ \\ M. F. Hasler, Jan 26 2012


CROSSREFS

Cf. A117537, A117538, A117539, A079630, A088749, A088750, A054540.
Sequence in context: A213267 A145977 A050729 * A104665 A094018 A183106
Adjacent sequences: A117533 A117534 A117535 * A117537 A117538 A117539


KEYWORD

hard,nonn,changed


AUTHOR

Gene Ward Smith, Mar 27 2006


EXTENSIONS

Extended by T. D. Noe, Apr 19 2010


STATUS

approved



