Question 988307
These are decreasing powers of 3 starting with {{{3^4}}}
{{{a[n]=3^(5-n)}}}
{{{a[1]=3^4=81}}}
{{{a[2]=3^3=27}}}
{{{a[3]=3^2=9}}}
{{{a[4]=3^1=3}}}
I){{{a[10]=3^(5-10)=3^(-5)=1/243}}}
II) {{{S=(3^9+3^8+3^7+3^6+3^5+3^4+3^3+3^2+3^1+3^0)/243=29524/243}}}
III) {{{S=(3^18+3^16+3^14+3^12+3^10+3^8+3^6+3^4+3^2+3^0)/3^15=435848050/14348907}}}