SERIESSUM(x; n; m; coefficients) = coefficient_1*x^n + coefficient_2*x^(n+m) + coefficient_3*x^(n+2*m) + ... + coefficient_i*x^(n+(i-1)*m)
SUMA SERIES(x;n;m;coeficientes) = coeficiente_1*x^n + coeficiente_2*x^(n+m) + coeficiente_3*x^(n+2m) +...+ coeficiente_i*x^(n+(i-1)m)