For some reason this hasn't been asked before and I can't seem to find an example. Here $R$ is a commutative ring.
Find a non-zero $R$-module $M$ such that $M \oplus M \cong M$
2026-03-29 13:41:13.1774791673
Give a non-zero $R$-module $M$ such that $M \oplus M \cong M$
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