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 A003018 M1178 #42 May 04 2018 23:41:19 %S A003018 1,1,2,4,9,20,47,111,270,664,1659,4184,10662,27367,70747,183925, %T A003018 480656,1261630,3324772,8792592,23327249,62067785,165586565 %N A003018 Number of distinct values taken by 3^3^...^3 (with n 3's and parentheses inserted in all possible ways). %D A003018 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A003018 F. Goebel and R. P. Nederpelt, <a href="http://www.jstor.org/stable/2316312">The number of numerical outcomes of iterated powers</a>, Amer. Math. Monthly, 80 (1971), 1097-1103. %H A003018 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 A003018 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 A003018 <a href="/index/Par#parens">Index entries for sequences related to parenthesizing</a> %H A003018 <a href="http://mathoverflow.net/questions/79442/number-of-distinct-values-taken-by-xx-x-with-parentheses-inserted-in-all-pos">MathOverflow discussion of related questions</a> %Y A003018 Cf. A002845, A003019, A145545, A145546, A145547, A145548, A145549, A145550, A000081. %K A003018 nonn,nice,more %O A003018 1,3 %A A003018 _N. J. A. Sloane_ %E A003018 a(12)-a(23) from _Jon E. Schoenfield_, Oct 11 2008