%I A058585
%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.
%Y A058585 Sequence in context: A032010 A032028 A127384 this_sequence A001573 A135307 
               A000083
%Y A058585 Adjacent sequences: A058582 A058583 A058584 this_sequence A058586 A058587 
               A058588
%K A058585 nonn
%O A058585 0,3
%A A058585 N. J. A. Sloane (njas(AT)research.att.com), Dec 26 2000