

A101627


Numerator of partial sums of a certain series.


5



1, 39, 241, 34883, 14039, 1516871, 7601151, 875425657, 7887002813, 7095769757767, 14199583385459, 75087685321529, 75113436870869, 927229349730873529, 927436191807263569, 305182576081725442901, 23479178371879154033, 37713848011377144613, 37717984058802320713, 135759786815564675620247
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OFFSET

1,2


COMMENTS

The denominators are given in A101628.
Second member (m=3) of a family defined in A101028.
The limit s=lim(s(n),n>infinity) with the s(n) defined below equals 8*sum(zeta(2*k+1)/3^(2*k),k=1..infinity) with Euler's (or Riemann's) zeta function. This limit is 12*(log(3)1) = 1.18334746...; see the AbramowitzStegun (given in A101028) reference p. 259, eq. 6.3.15 with z=1/3 together with p. 258.


LINKS

Table of n, a(n) for n=1..20.
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
Wolfdieter Lang, Rationals s(n) and more.


FORMULA

a(n)=numerator(s(n)) with s(n)=24*sum(1/((3*k1)*(3*k)*(3*k+1)), k=1..n).


EXAMPLE

s(3)= 24*(1/(2*3*4)+ 1/(5*6*7) + 1/(8*9*10)) = 241/210, hence a(3)=241 and A101628(3)=210.


MATHEMATICA

Numerator[Accumulate[Table[8/(9k^3k), {k, 20}]]]


PROG

(PARI) a(n) = numerator(24*sum(k=1, n, 1/((3*k1)*(3*k)*(3*k+1))));


CROSSREFS

Cf. A101028 (m=2), A101629 (m=4), A101631 (m=5).
Cf. A101628 (denominators).
Sequence in context: A266104 A190538 A190606 * A229639 A070146 A327344
Adjacent sequences: A101624 A101625 A101626 * A101628 A101629 A101630


KEYWORD

nonn,frac,easy


AUTHOR

Wolfdieter Lang, Dec 23 2004


EXTENSIONS

More terms from Michel Marcus, Mar 01 2022


STATUS

approved



