This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A213619 #19 Nov 28 2021 03:12:01 %S A213619 1,2,65536 %N A213619 Let m be the n-th hyperoperation applied to n (see A189896). a(n) is the m-th hyperoperation applied to n and m. %C A213619 Let bn=A189896(n), that is, bn=H_n(n,n), where H_n is the n-th hyperoperation. %C A213619 Then %C A213619 a(n) = H_bn(n,bn), hence %C A213619 a(0) = H_b0(0,b0) = H_1(0,1) = 0+1 = 1, %C A213619 a(1) = H_b1(1,b1) = H_2(1,2) = 1*2 = 2, %C A213619 a(2) = H_b2(2,b2) = H_4(2,4) = 2^2^2^2 = 65536, and %C A213619 a(3) is too large to include here. %F A213619 a(n) = H_H_n(n,n)(n,H_n(n,n)). %e A213619 a(0) = H_H_0(0,0)(0,H_0(0,0)) = H_1(0,1) = 0+1 = 1. %e A213619 a(1) = H_H_1(1,1)(1,H_1(1,1)) = H_2(1,1+1) = 1*(1+1) = 2. %e A213619 a(2) = H_H_2(2,2)(2,H_2(2,2)) = H_4(2,2*2) = H_3(2,H_3(2,H_3(2,2))) = 2^2^2^2 = 2^2^4 = 2^16 = 65536. %Y A213619 Cf. A189896. %K A213619 nonn,bref %O A213619 0,2 %A A213619 _Jens Ahlström_, Jun 16 2012