[1] Budapest Univ Technol & Econ, Inst Math, Dept Stochast, H-1111 Budapest, Hungary
[2] Budapest Univ Technol & Econ, Dept Comp Sci & Informat Theory, H-1111 Budapest, Hungary
[3] MTA BME Lendulet Arithmet Combinator Res Grp, ELKH, H-1111 Budapest, Hungary
[4] Nanjing Normal Univ, Sch Math Sci, Nanjing 210023, Peoples R China