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 A003008 M1147 #25 Jan 05 2025 10:15:01 %S A003008 1,1,2,4,8,17,39,90,213 %N A003008 Number of n-level ladder expressions with A030798. %D A003008 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A003008 R. K. Guy and J. L. Selfridge, <a href="http://www.jstor.org/stable/2319392">The nesting and roosting habits of the laddered parenthesis</a>, Amer. Math. Monthly 80 (8) (1973), 868-876. %H A003008 R. K. Guy and J. L. Selfridge, <a href="/A003018/a003018.pdf">The nesting and roosting habits of the laddered parenthesis</a>. (annotated cached copy) %H A003008 <a href="/index/Par#parens">Index entries for sequences related to parenthesizing</a> %Y A003008 Cf. A082499. %K A003008 nonn,more %O A003008 1,3 %A A003008 _N. J. A. Sloane_