S ( v → w ) = d ( v )  ∏ i ∈ P ( v , w )   d ( i )     F ( c )       ( 2 )    MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqWGtbWucqGGOaakcqWG2bGDcqGHsgIRcqWG3bWDcqGGPaqkcqGH9aqpdaWcaaqaaiabdsgaKjabcIcaOiabdAha2jabcMcaPaqaamaarababaGaemizaqMaeiikaGIaemyAaKMaeiykaKcaleaacqWGPbqAcqGHiiIZcqWGqbaucqGGOaakcqWG2bGDcqGGSaalcqWG3bWDcqGGPaqkaeqaniabg+GivdaaaOGaemOrayKaeiikaGIaem4yamMaeiykaKIaaCzcaiaaxMaadaqadaqaaiabikdaYaGaayjkaiaawMcaaaaa@5189@