Partial Progression?

Calculus Level 4

Let $$a_1, a_2, a_3, \ldots$$ be an arithmetic progression with first term $$A$$ and a non-zero common difference $$D$$.

Is the series $$a_1 + a_2+a_3+ \cdots$$ Cesaro summable? If yes, find the value of this divergent sum in terms of $$A$$ and/or $$D$$.

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