(1-1/3)×(1-1/5)×(1-1/7)×(1-1/9)×(1-1/11))×(1-1/13)×(1-1/15)=
(2*4*6*.*14)/(3*53*7*.15)=(2^7*2*4*6)/(9*11*13*15)
=(2^11)/(3*11*13*15)=2048/63135