Are these OK?
I'd be lying if I said I didn't think of it.
I'd be lying if I said I didn't think about it.
I'd be lying if I told you I didn't think about it.
I'd be lying if I told you I hadn't thought about it.

Question

Answer

The first one is odd. "I didn't think of it" means that it didn't even cross your mind. "I didn't think about it" means you haven't spent any time thinking about it. Anyway, "I'd be lying if I said I didn't think of it." is awkward. Use "about" instead.

Answer

Each of these sentences is grammatically correct. However, the first one does sound a bit less natural; I would use the second one instead. The third and fourth sound perfectly okay.

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