Abstract Submanifolds of the Euclidean spaces satisfying
equality in the basic Chen's inequality have, as is known, many
interesting properties. In this paper, we discuss on such
submanifolds the curvature conditions of the form $E_2\cdot
F_4=0$, where $E_2$ is the Ricci or the Einstein curvature
operator, $F_4$ is any of the standard curvature operators $R, Z,
P, K, C$, and $E_2$ acts on $F_4$ as a derivation.
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