OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..400
Eric Weisstein's World of Mathematics, Power Tower
Wikipedia, Knuth's up-arrow notation
Wikipedia, Tetration
FORMULA
E.g.f.: (x+1)^^9.
MAPLE
f:= proc(n) f(n):= `if`(n=0, 1, (x+1)^f(n-1)) end:
a:= n-> n!*coeff(series(f(9), x, n+1), x, n):
seq(a(n), n=0..25);
MATHEMATICA
f[n_] := f[n] = If[n == 0, 1, (x + 1)^f[n - 1]];
a[n_] := n!*SeriesCoefficient[f[9], {x, 0, n}];
Table[a[n], {n, 0, 25}] (* Jean-François Alcover, May 30 2018, from Maple *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 19 2016
STATUS
approved