This is geometric series with first term `a_1=1` and ratio `r=3`.

Sum of the first `n` terms of geometric series is

`S_n=a_1 (r^n-1)/(r-1)`

**Hence sum of the first 20 terms is** ` `

`S_20=(3^20-1)/(3-1)=(3^20-1)/2=1743392200`

This is geometric series with first term `a_1=1` and ratio `r=3`.

Sum of the first `n` terms of geometric series is

`S_n=a_1 (r^n-1)/(r-1)`

**Hence sum of the first 20 terms is** ` `

`S_20=(3^20-1)/(3-1)=(3^20-1)/2=1743392200`