Can you figure out easy-looking math sum in 30 seconds by remembering the special rule?

The answer to this mathematical brain teaser is NOT 40 - can YOU solve it in 30 seconds by remembering the special rule?
IEEE

A Fixed-Time Proximal Gradient Neurodynamic Network With Time-Varying Coefficients for Composite Optimization Problems and Sparse Optimization Problems With Log-Sum Function

Abstract: This article presents a novel proximal gradient neurodynamic network (PGNN) for solving composite optimization problems (COPs). The proposed PGNN with time-varying coefficients can be ...
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This math problem has never failed, not once

The Collatz Conjecture is defined by a rule simple enough for a child to follow. No matter what number you start with, the process always appears to end the same way — and it has never been observed ...
IEEE

An Iterative Threshold Algorithm of Log-Sum Regularization for Sparse Problem

Abstract: The log-sum function as a penalty has always been drawing widespread attention in the field of sparse problems. However, it brings a non-convex, non-smooth and non-Lipschitz optimization ...
Indiatimes

Einstein was fascinated by this math problem because it had no solution

There is a tendency to imagine genius as smooth and uninterrupted. As if the great thinkers moved from one insight to the next without pause. Albert Einstein does not quite fit that picture. For all ...
The Korea Herald

Six-decade math puzzle solved by Korean mathematician

A Korean mathematician has won international recognition for solving a geometry puzzle that had resisted proof for nearly six decades. US magazine Scientific American named the research by Baek ...