Numbers not Expressible as Sum of Fewer than 19 Fourth Powers/Historical Note

Historical Note on Numbers not Expressible as Sum of Fewer than 19 Fourth Powers
It was noted by that there were no other positive integers needing $19$ fourth powers to express them less than $4100$.

This limit was reported by in his  of $1997$.

, and  extended this to $10^{245}$ in $2000$.

Subsequently,, and  showed that the sequence is complete beyond $10^{220}$.