Pair of Ulam Numbers differing by One/Historical Note

Historical Note on Pair of Ulam Numbers differing by One
According to in his  of $1997$, the Ulam numbers were investigated up to $20 \, 000$ terms by a, whom this contributor has not been able to identify.

Notwithstanding the scarcity of pairs of Ulam numbers which differ by $1$, more than $60\%$ of pairs differ by $2$.