A way to prove the irrationality of Zeta(4)
  The proof of the irrationality of Zeta(5) is a long standing open problem, but here only the case of Zeta(4) = (Pi^4)/90 is considered. The present paper suggests an approach for the irrationality of Zeta(4) along the lines of those known for proving the irrationality of Zeta(3). 
Dirk Huylebrouck
math.NT