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 A098820 #16 Jun 16 2025 08:41:06 %S A098820 1,1,2,4,4,8,8,8,8,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16, %T A098820 16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16, %U A098820 16,16,16,16,16,16,16,16 %N A098820 Periodicity of entries in the first row of a Laver Table of size 2^n. %C A098820 All sequence elements are powers of 2. The first n for which a(n)=32 is at least A(9,A(8,A(8,255))), where A denotes the Ackermann function (R. Dougherty). If a rank-into-rank exists, then the sequence is diverging (R. Laver). %H A098820 Richard Laver, <a href="https://arxiv.org/abs/math/9204204">On the Algebra of Elementary Embeddings of a Rank into Itself</a>, arXiv:math/9204204 [math.LO], 1992; Advances in Mathematics 110, p. 334, 1995 %H A098820 Wikipedia, <a href="https://en.wikipedia.org/wiki/Laver_table">Laver table</a> %e A098820 a(4)=4 because the entries in the first row of the Laver table of size 4^2=16 are 2,12,14,16,2,12,14,16,2,12,14,16,2,12,14,16 (and thus repeat with a periodicity of 4). %K A098820 nonn %O A098820 0,3 %A A098820 _Christian Schroeder_, Oct 08 2004 %E A098820 More terms from _Adam P. Goucher_, Dec 18 2013