R/2×(1+R/2)^{2n}}÷{(6+5R/4)×((1+R/2) ^{2n }-1)} { R/2×(1+R/2)^{2n} }÷{(2+R/4)×((1+R/2) ^{2n}-1)} { R/2×(1+R/2)^{2n} }÷{(1+R/2) ^{2n}-1} { ((1+R/2)^{2}-1)×(1+R/2)^{2n} }÷{(1+R/2) ^{2n}-1}