This is a function I wrote from my mind that would match all integers of a function a(x), yet remain continuous and differentiable. However, I think that the function's complexity might be causing this error: sum does not converge. I don't know what that means. The function works if a(x)=(-1)^x, but that's probably because that makes the function cos(pi*x). Anyway I can test this further or make a work around?
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