So far I factored out x^(6n) from the sum of a_(1+6n)x, a_(2+6n)x^2 .... a_(6+6n)x^6. I was thinking about rewriting the power series x^(6n) as 1/(1-x^6) but not sure what do.
Suppose the series Σ-oan&n has the property that an+,-an for all n 20. (a) Find a formula or a function that equals our series over its interval of convergence (b) Find the interval of convergence of the series
