Pictures from the On-Line Encyclopedia of Integer Sequences
oeis.org
oeis.org
http://arxiv.org/abs/1101.4470
Numberphile has a video about it:
> Poster illustrating A259934 and A263267. Subtract the number of divisors from a number in the tree, and you get the number under it. Shows the inter-connectedness of the OEIS. (Michael De Vlieger and Antti Kartunen)