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 A075824 #22 Feb 26 2022 16:12:43 %S A075824 9,11,17,19,21,25,27,33,35,39,41,43,45,49,51,53,57,59,65,67,69,71,73, %T A075824 75,77,79,81,83,85,87,89,91,93,95,97,99,103,105,107,109,111,113,115, %U A075824 117,121,123,129,131,133,135,137,139,141,143,145,147,149,151,153,155,157 %N A075824 Odd numbers that cannot be expressed as 2^k - 3^m where k and m are integers. %C A075824 All listed terms can be certified by considering 2^k - 3^m modulo 2552550. [_Max Alekseyev_, Feb 08 2010] %D A075824 R. K. Guy, Unsolved Problems in Number Theory, D9. %D A075824 T. N. Shorey and R. Tijdeman, Exponential Diophantine Equations, Cambridge University Press, 1986. %H A075824 T. Metsankyla, <a href="https://doi.org/10.1090/S0273-0979-03-00993-5">Catalan's Conjecture : Another old Diophantine problem solved</a>, Bull. Amer. Math. Soc. 41 (2004), 43-57. %H A075824 Wikipedia, <a href="http://www.wikipedia.org/wiki/Catalan%27s_conjecture">Catalan's conjecture</a> %e A075824 5 doesn't belong to the sequence because it can be expressed as 2^3 - 3^1. %Y A075824 Cf. A074981, A192110, A328077. %K A075824 nonn %O A075824 1,1 %A A075824 _Felice Russo_, Oct 14 2002 %E A075824 Inserted "odd" in definition. - _N. J. A. Sloane_, Jan 30 2009 %E A075824 _Jon E. Schoenfield_ observed that 49 was missing, Jan 30 2009 %E A075824 More terms from _Max Alekseyev_, Feb 08 2010