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 A053169 #20 Dec 25 2022 19:54:45 %S A053169 4,7,9,11,12,13,15,17,18,20,21,22,23,24,25,28,29,30,31,32,33,34,35,38, %T A053169 39,40,41,42,43,44,45,46,47,48,49,50,51,53,54,55,56,57,58,60,61,63,64, %U A053169 65,66,67,68,70,71,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100 %N A053169 A paradoxical sequence: a positive integer n is in this sequence if and only if n is not in sequence A_n in the database. %C A053169 "Not in sequence A_n" means not in the full list of terms, not simply in the list of terms visible in the entry. %C A053169 The paradox is of course: is 53169 in this sequence? %D A053169 Smullyan, Raymond M, What is the name of this book? : The riddle of Dracula and other logical puzzles, Englewood Cliffs, NJ : Prentice-Hall, c1978, see puzzle 163. %H A053169 <a href="/index/Se#selfies">Index entries for sequences whose definition involves A_n (or An)</a>. %e A053169 Sequence A000001 contains 1, so 1 is not in the sequence; A000002 contains 2, so 2 is not in the sequence; ... %Y A053169 Cf. A107357. %Y A053169 Complement of A053873. %K A053169 nonn,nice %O A053169 1,1 %A A053169 Miklos Szabo (mike(AT)ludens.elte.hu), _N. J. A. Sloane_, Feb 29 2000 %E A053169 Thanks to _Alexander Hulpke_ for the information that 19 is in A000019. %E A053169 Extended to n=100 by _N. J. A. Sloane_, May 26 2007