Twelve new primitive binary trinomials
  We exhibit twelve new primitive trinomials over GF(2) of record degrees $42643801$, $43112609$, and $74207281$. In addition we report the first Mersenne exponent not ruled out by Swan's theorem - namely $57885161$ - for which no primitive trinomial exists. This completes the search for the currently known Mersenne prime exponents. 
Richard P. Brent and Paul Zimmermann
math.NT