Respuesta :

LammettHash
Each next term is being multiplied by 5. Assuming there are only 4 terms to the sum, you have

[tex]10+50+250+1250=10\times5^0+10\times5^1+10\times5^2+10\times5^3=\displaystyle\sum_{i=0}^310\times5^i[/tex]