24. Let be a non-principal character modulo . Prove:
(i) When , the series converges, and when ,
(ii) When ,
(iii) When ,
(iv) When ,
Solution
24. (i) The first part uses Question 21, the second part is a special case of Question 2 of Exercise Three in Chapter 8;
(ii) Prove similarly to Question 3 of Exercise Three in Chapter 8; (iii) Use (i); (iv) Use (i) or (iii).
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