P ( E ) = p × ( 1 − 1 n − m + 1    )   h − m   ≃ p       ( 20  )    MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqWGqbaucqGGOaakieqacqWFfbqrcqGGPaqkcqGH9aqpcqWGWbaCcqGHxdaTdaqadaqaaiabigdaXiabgkHiTmaalaaabaGaeGymaedabaGaemOBa4MaeyOeI0IaemyBa0Maey4kaSIaeGymaedaaaGaayjkaiaawMcaamaaCaaaleqabaGaemiAaGMaeyOeI0IaemyBa0gaaOGaeS4qISJaemiCaaNaaCzcaiaaxMaadaqadaqaaiabikdaYiabicdaWaGaayjkaiaawMcaaaaa@4A3A@