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 A005268 M1233 #27 Dec 26 2021 21:14:36 %S A005268 1,1,2,4,10,31,120,578,3422,24504,208833,2086777,24123293,318800755, %T A005268 4766262421,79874304340,1488227986802 %N A005268 Number of elementary sequences of length n. %C A005268 In Fishburn-Roberts (1989) it is stated that no recurrence is known. - _N. J. A. Sloane_, Jan 04 2014 %D A005268 Fishburn, Peter C.; Roberts, Fred S., Uniqueness in finite measurement. Applications of combinatorics and graph theory to the biological and social sciences, 103--137, IMA Vol. Math. Appl., 17, Springer, New York, 1989. MR1009374 (90e:92099) %D A005268 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A005268 Fishburn, Peter C.; Roberts, Fred S., <a href="/A005269/a005269.pdf">Uniqueness in finite measurement</a>, in Applications of combinatorics and graph theory to the biological and social sciences, 103--137, IMA Vol. Math. Appl., 17, Springer, New York, 1989. MR1009374 (90e:92099). [Annotated scan of five pages only] %H A005268 Peter C. Fishburn, Fred S. Roberts, <a href="http://dx.doi.org/10.1016/0166-218X(93)90236-H">Elementary sequences, sub-Fibonacci sequences</a>. Discrete Appl. Math. 44 (1993), no. 1-3, 261-281. %H A005268 Sean A. Irvine, <a href="/A005268/a005268.txt">Complete set of sequences for a(11)</a> %Y A005268 Sequences in the Fishburn-Roberts (1989) article: A005269, A005268, A234595, A005272, A003513, A008926. %K A005268 nonn,more %O A005268 1,3 %A A005268 _N. J. A. Sloane_ %E A005268 a(11) corrected and a(12)-a(14) from _Sean A. Irvine_, Apr 27 2016 %E A005268 a(15)-a(17) from _Bert Dobbelaere_, Dec 28 2020