OFFSET
0,2
COMMENTS
a(n) is divisible by 2^n and congruent to 1, 2, 4, 5, 7 or 8 mod 9.
EXAMPLE
1, -2/3, 16/15, -424/105, 2944/105, -70240/231, 70873856/15015, ...
MATHEMATICA
nmax = 30; Clausen[n_] := Times @@ Select[Divisors[n] + 1, PrimeQ]; t = Join[{1}, Table[Numerator[BernoulliB[n, 1/2] - (n + 1)*EulerE[n, 0]]/Clausen[n], {n, 1, nmax}]]; dt = Table[Differences[t, n], {n, 0, nmax}]; Diagonal[dt] // Numerator
CROSSREFS
KEYWORD
frac,sign,easy
AUTHOR
Jean-François Alcover and Paul Curtz, Sep 11 2013
STATUS
approved