Iv. Ostrovskii, POWER-SERIES HAVING TAILS WITH ONLY REAL NONPOSITIVE ZEROS, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 325(12), 1997, pp. 1257-1262
If for all sufficiently large n the n(th) tail of the power series of
an entire function f has only real nonpositive zeroes, then logM(r,f)l
ess than or equal to 1/2log2(logr)(2)+Omicron(logr), r-->infinity, Thi
s bound is close to the title best possible.