OFFSET
0,2
EXAMPLE
For n=1, the 1st derivative of x^(x^x) is x^(x^x+x-1) + x^(x^x+x)*log(x) + x^(x^x+x)*log^2(x), so a(1) = 3.
MATHEMATICA
Join[{1}, Length /@ Rest[NestList[Expand[D[#, x]] &, x^x^x, 42]]]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Reshetnikov, Oct 05 2017
STATUS
approved