Annual Appeal: Please make a donation to keep the OEIS running. In 2017 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS").
These numbers are one step nearer (than those of A262509) to the root (zero) of the tree where the parent-child relation is given by A049820(child) = parent. Like the terms of A262509, they are also vertices in the infinite trunk of that tree. Cf. A259934.