[seqfan] Unknown sequence related to Bernoulli-numbers/zeta() at negative arguments

[Gottfried Helms]

Hi -
  analyzing some matrix-summation-scheme [*1] I come across two
  sequences, which might be understood as a0(n) "of order 0",
  a1(n) of "order 1" -  and I shall also later (by generalization
  of the computations) be confronted with more sequences a2(n),
  a3(n), a4(n),... similar/related to the first two ones, but
  just of "higher orders" - but don't have that coefficients yet.

  The sequence a0(0) is obvious - this is the sequence of
  zeta-values at nonpositive arguments.
  I suspect, the sequence a1(n) is somehow a convolution, or
  transformation of that but do not have any really convincing idea;
  however in the third column I compute 2*a1(k) + a0(k-1) and find
  at least, that each second one is exactly a bernoulli-number.

  Here is the table of sequences:

             a0(k)          a1(k)            2 a1(k) + a0(k-1)
--------------------------------------------------------------
             0                .                       .
             0                0                       .
          -1/2                0                       0
         -1/12              1/4                       0
             0              1/8                        1/6
         1/120             1/48                    1/24
             0            -1/48                       -1/30
        -1/252            -1/96                   -1/48
             0             1/72                        1/42
         1/240         101/8640                101/4320
             0           -3/160                        -1/30
        -1/132          -13/576                 -13/288
             0             1/24                         5/66
     691/32760         402/6079                804/6079
             0        -691/5040                        -691/2730
         -1/12       -2357/8640              -2357/4320
             0              5/8                         7/6

 The sequences are taken by approximation of lists of coefficients,
 which I find by a linear regression based on data which must be
 computed by a very time-consuming procedure with high precision.

 The sequence of regression-coefficients a1(n) is thus basically a
 sequence of real numbers, but approximations to rational numbers with
 at most 4-digit-denominators give then the above guesses.
 Because of the time and precision required for the computation of the
 underlying data I unfortunately cannot easily produce more
 (somehow reliable) such sequence-entries.

 For that found entries in s1() I'm pretty sure that that values are
 the most plausible ones, but single ones with the higher denominators
 might be incorrect guesses.


 So does someone have an idea, how possibly a1(n) could be composed
 by the bernoulli-numbers/zetas-at-negative-arguments?

 Gottfried

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 [*1] testing number-theoretical properties of my summation-method
 with the matrix of factorially scaled Eulerian numbers for summation
   * of 1/k^2 (arriving at a0(n)) and
   * of 1/k^3 (arriving at a1(n)).