This is too long for a comment. It's already been established that the mathematician being referred to is Simon Sidon. The book "Mathematical Cultures: The London Meetings 2012–2014ő" attributes the following quote (which is sourced to a video interview) to P. Erdős about Simon Sidon:

… In 1934 I met a Hungarian mathematician called Sidon who worked mostly in trigonometric series. And he was a very good mathematician, but he was a bit crazier than the average … mathematician …. In fact he was a bordeline schizophrenic. They tell about him that he usually talked this way to you (turning away from the audience), he turned towards the wall and talked. But when he talked about mathematics he talked sense. And he even made it into a Hungarian anecdote book, because once when in 1937, when Turán and I visited him — he (Sidon) also had a persecution complex — so he opened a door a crack and said ‘Please come at another time and to another person’ … ‘Kérem, jőjjenek inkább máskor és máshoz!’ It sounds better in Hungarian.

This is too long for a comment. It's already been established that the mathematician being referred to is Simon Sidon. The book "Mathematical Cultures: The London Meetings 2012–2014" attributes the following quote (which is sourced to a video interview) to P. Erdős about Simon Sidon:

… In 1934 I met a Hungarian mathematician called Sidon who worked mostly in trigonometric series. And he was a very good mathematician, but he was a bit crazier than the average … mathematician …. In fact he was a bordeline schizophrenic. They tell about him that he usually talked this way to you (turning away from the audience), he turned towards the wall and talked. But when he talked about mathematics he talked sense. And he even made it into a Hungarian anecdote book, because once when in 1937, when Turán and I visited him — he (Sidon) also had a persecution complex — so he opened a door a crack and said ‘Please come at another time and to another person’ … ‘Kérem, jöjjenek inkább máskor és máshoz!’ It sounds better in Hungarian.

This is too long for a comment. It's already been established that the mathematician being referred to is Simon Sidon. The book "Mathematical Cultures: The London Meetings 2012-2014" attributes the following quote (which is sourced to a video interview) to P. Erdos about Simon Sidon:

This is too long for a comment. It's already been established that the mathematician being referred to is Simon Sidon. The book "Mathematical Cultures: The London Meetings 2012–2014ő" attributes the following quote (which is sourced to a video interview) to P. Erdős about Simon Sidon:

… In 1934 I met a Hungarian mathematician called Sidon who worked mostly in trigonometric series. And he was a very good mathematician, but he was a bit crazier than the average … mathematician …. In fact he was a bordeline schizophrenic. They tell about him that he usually talked this way to you (turning away from the audience), he turned towards the wall and talked. But when he talked about mathematics he talked sense. And he even made it into a Hungarian anecdote book, because once when in 1937, when Turán and I visited him — he (Sidon) also had a persecution complex — so he opened a door a crack and said ‘Please come at another time and to another person’ … ‘Kérem, jőjjenek inkább máskor és máshoz!’ It sounds better in Hungarian.