What is right hand side limit of Dirichlet eta function of -1?

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What is right hand side limit of Dirichlet eta function of -1 ? Left hand side ia 1/4, right hand side doesn't exist as I understand, motivation : https://en.wikipedia.org/wiki/1_%2B_2_%2B_3_%2B_4_%2B_%E2%8B%AF#Zeta_function_regularization