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 A352196 #51 May 25 2025 19:48:52 %S A352196 0,2,4,3,5,4,6,3,6,5,6,4,6,4,4,4,6,4,7,4,4,5,6,4,8,4,6,4,7,4,6,5,7,6, %T A352196 4,4,7,6,4,4,7,4,5,5,4,5,6,4,6,5,5,4,9,5,8,4,6,6,6,4,7,5,4,5,4,5,8,5, %U A352196 8,4,7,4,6,6,7,6,7,4,7,4,9,6,8,4,5,5,7,5,9,4,4,5,5,5,6,5,5,6,6,5,8,5,7,4,4,6,5,5,8,6,7,4,8,5,7,5,4,7,6 %N A352196 a(n) = number of steps for the standard mod-n Ackermann function to stabilize to a set consisting of only one value, or -1 if it does not stabilize. %C A352196 This was Stan Wagon's Problem of the Week #1340, from March 2022, which in turn was based on a 1993 Monthly problem of Jon Froemke and Jerrold Grossman. %C A352196 Stan Wagon mentions that Mark Rickert has found the first 8 million terms (see link), and the only one that does not stabilize is n = 1969 where it becomes periodic with period 2 after 8 steps. So a(1969) = -1. %C A352196 [Needs program(s), b-file. - _N. J. A. Sloane_, May 25 2025] %H A352196 Jon Froemke and Jerrold W. Grossman, <a href="https://www.jstor.org/stable/2323780">A Mod-n Ackermann Function, or What's So Special About 1969?</a>, The American Mathematical Monthly, Vol. 100, No. 2 (February 1993), pp. 180-183; <a href="https://www.researchgate.net/publication/2795061_Ackermann_Function_or_What's_So_Special_about_1969">ResearchGate link</a>. %H A352196 Mark Rickert, <a href="/A352196/a352196-8M.gz">The first 8 million terms of A085119</a> [a gzipped file], March 2022. %H A352196 Stan Wagon, <a href="/A352196/a352196.pdf">Problem of the Week POW #1340: Modular Ackermann</a>, March 2022. %H A352196 Stan Wagon, <a href="/A352196/a352196_1.pdf">Problem of the Week POW #1340: Solution</a>, March 2022. %Y A352196 Cf. A085119. %K A352196 nonn %O A352196 1,2 %A A352196 _N. J. A. Sloane_, Mar 23 2022 %E A352196 "Standard" added to definition by _N. J. A. Sloane_, May 25 2025 to be consistent with the Froemke-Grossman (1993) article.