%I #39 Jan 11 2020 15:57:46
%S 4,7,12,64,
%T 13407807929942597099574024998205846127479365820592393377723561443721764030073546976801874298166903427690031858186486050853753882811946569946433649006084096
%N a(n) = H_n(4,3) where H_n is the n-th hyperoperator.
%C See A054871 for definitions and key links.
%e a(0) = H_0(4,3) = 3+1 = 4;
%e a(1) = H_1(4,3) = 4+3 = 7;
%e a(2) = H_2(4,3) = 4*3 = 12;
%e a(3) = H_3(4,3) = 4^3 = 64;
%e a(4) = H_4(4,3) = 4^^3 = 4^4^4 = 4^256 = ... ;
%e a(5) = H_5(4,3) = 4^^^3 = 4^^4^^4 = 4^^(4^4^4^4) = 4^^(4^4^256) = ... .
%Y Cf. A054871.
%K nonn
%O 0,1
%A _Natan Arie Consigli_, Apr 18 2015
%E First term corrected and hyperoperator notation implemented by _Danny Rorabaugh_, Oct 20 2015