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 A058585 #5 May 02 2013 00:19:42 %S A058585 1,1,2,4,9,23,63,177,514,1526,4624,14230,44357,139779,444557,1425151, %T A058585 4600338,14939849,48778197,160019884,527200711,1743607825,5786756469, %U A058585 19266336882,64331275266,215377539119,722840378041,2431459847363 %N A058585 An approximation to A000084(n). %D A058585 J. Riordan and C. E. Shannon, The number of two-terminal series-parallel networks, J. Math. Phys., 21 (1942), 83-93. Reprinted in Claude Elwood Shannon: Collected Papers, edited by _N. J. A. Sloane_ and A. D. Wyner, IEEE Press, NY, 1993, pp. 560-570. %F A058585 a(n) = floor(u(n)) where u(n) has g.f. (1/2)*(5-3*x-2*x^2-sqrt(9-30*x-11*x^2+12*x^3+4*x^4)). %Y A058585 Cf. A000084, A001573, A093156. %K A058585 nonn %O A058585 0,3 %A A058585 _N. J. A. Sloane_, Dec 26 2000