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 A001573 M1190 N0460 #19 Jun 27 2015 15:07:53 %S A001573 1,2,4,9,23,63,177,514,1527,4625,14230,44357,139779,444558,1425151, %T A001573 4600339,14939849,48778197,160019885,527200711 %N A001573 Another approximation to A000084(n). %C A001573 Appears to have been calculated with very low precision. A093156 is a better version. - Pab Ter (pabrlos(AT)yahoo.com), May 11 2004 %D A001573 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. %D A001573 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). %D A001573 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A001573 J. Riordan and C. E. Shannon, <a href="/A000084/a000084_1.pdf">The number of two-terminal series-parallel networks</a> (annotated scanned copy) %Y A001573 Cf. A000084, A058585. %K A001573 nonn,more %O A001573 1,2 %A A001573 _N. J. A. Sloane_