%I #9 Oct 29 2021 05:04:03
%S 0,1,1,2,1,1,3,4,1,1,4,27,16,1,1,5,256,19683,256,1,1,6,3125,
%T 4294967296,7625597484987,65536,1,1,7,46656,298023223876953125,
%U 340282366920938463463374607431768211456
%N Square array, read by antidiagonals, where T(n,k)=n^^k for n>=0, k>=1.
%C n^^k is defined the left-associative way: n^^2=n^n, n^^3=(n^n)^n=n^(n^2), n^^4=((n^n)^n)^n=n^(n^3), and in general n^^k=n^(n^(k-1)).
%C More terms on Munafo website.
%H Robert Munafo, <a href="http://mrob.com/pub/math/hyper4.html">Hyper4 Iterated Exponential Function</a>.
%e Array begins:
%e 0,1,1,1,1,1,...
%e 1,1,1,1,1,1,...
%e 2,4,16,256,65536,...
%e 3,27,19683,...
%e 4,256,4294967296,...
%e 5,3125,...
%e 6,46656,...
%t T[n_, k_] := If[n == 0, Boole[k != 0], n^(n^k)]; Table[T[k, n - k], {n, 0, 7}, {k, n, 0, -1}] // Flatten (* _Amiram Eldar_, Oct 29 2021 *)
%Y Cf. A171882.
%K nonn,tabl
%O 0,4
%A _Robert Munafo_, Jan 21 2010