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 A067652 #31 Mar 27 2020 10:14:46 %S A067652 4,5,6,8,16,65536 %N A067652 a(n) = H_n(2,3) = H_(n-1)(2,4) where H_n is the n-th hyperoperator. %C A067652 Originally named "2 plus 3, twice 3, 2 to the power of 3, etc." %C A067652 For hyperoperator definitions and links, see A054871. %C A067652 For nonnegative n, H_(n)(2,3) = H_(n-1)(2,H_(n-1)(2,2)) = H_(n-1)(2,4) or in the clearer square bracket notation: 2[n]3 = 2[n-1]2[n-1]2 = 2[n-1]4. - _Natan Arie Consigli_, Dec 07 2015 %e A067652 H_0(2,3) = 3+1 = 4; %e A067652 H_1(2,3) = 2+3 = 5; %e A067652 H_2(2,3) = 2*3 = 6; %e A067652 H_3(2,3) = 2^3 = 2*2*2 = 2*4 = H_2(2,4) = 8; %e A067652 H_4(2,3) = 2^^3 = 2^2^2 = 2^4 = H_3(2,4) = 16; %e A067652 H_5(2,3) = 2^^^3 = 2^^2^^2 = 2^^4 = H_4(2,4) = 2^2^2^2 = 2^16 = 65536; %e A067652 H_6(2,3) = 2^^^^3 = 2^^^2^^^2 = 2^^^4 = H_5(2,4) = 2^^2^^2^^2 = 2^^65536 = 2^2^...^2^2, with 65536 2's. %o A067652 (Haskell) f a 0 = 2 + a / f 0 1 = 0 / f 0 n = 1 / f a n = f (f (a-1) n) (n-1) %Y A067652 Cf. A054871. %K A067652 nonn,bref %O A067652 0,1 %A A067652 Ashley Yakeley (ashley(AT)yakeley.org), Feb 03 2002 %E A067652 Hyperoperator notation, new initial term, and examples by _Danny Rorabaugh_, Oct 14 2015 %E A067652 Sequence merged with H_(n)(2,4) by _Natan Arie Consigli_, Dec 07 2015