%I A001572 M2500 N0989
%S A001572 1,1,1,1,3,5,17,41,127,365,1119,3413,10685,33561,106827,342129,
%T A001572 1104347,3584649,11701369,38374065,126395259,417908329,1386618307,
%U A001572 4615388353,15407188529,51569669429,173033992311,581905285089,1961034571967
%N A001572 Related to series-parallel networks.
%C A001572 Contribution from Gary W. Adamson (qntmpkt(AT)yahoo.com), Sep 27 2008: 
               (Start)
%C A001572 Starting (1, 1, 1, 3, 5, 17,...) = the INVERTi transform of A000084: 
               (1, 2, 4, 10, 24, 66,...).
%C A001572 Equals left border of triangle A144962 (End)
%D A001572 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A001572 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001572 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 A001572 G.f.: 1 - Sum_{k=1..inf} a(k)*x^k = Product_{n=1..inf} (1-x^n)^A000669(n).
%Y A001572 A000084, A144962 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Sep 27 
               2008]
%Y A001572 Sequence in context: A148522 A141160 A113275 this_sequence A131342 A005142 
               A165452
%Y A001572 Adjacent sequences: A001569 A001570 A001571 this_sequence A001573 A001574 
               A001575
%K A001572 nonn,easy
%O A001572 0,5
%A A001572 N. J. A. Sloane (njas(AT)research.att.com).