%I A032123
%S A032123 1,1,4,10,38,126,472,1716,6470,24310,92504,352716,1352540,5200300,
%T A032123 20060016,77558760,300546630,1166803110,4537591960,17672631900,
%U A032123 68923356788,269128937220,1052049834576,4116715363800
%N A032123 Number of 2n-bead black-white reversible strings with n black beads.
%H A032123 C. G. Bower, <a href="transforms2.html">Transforms (2)</a>
%H A032123 N. J. A. Sloane, <a href="classic.html#LOSS">Classic Sequences</a>
%F A032123 n odd: C(2n-1, n-1); n even: C(2n-1, n-1) + C(n-1, n/2-1)
%F A032123 "BIK[ n ](2n-1)" (reversible, indistinct, unlabeled, n parts, 2n-1 elements) 
               transform of 1, 1, 1, 1...
%F A032123 E.g.f.: exp(x)*cosh(x)*BesselI(0, 2*x). - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Apr 07 2005
%Y A032123 Central column of Losanitsch's triangle A034851.
%Y A032123 Sequence in context: A046562 A149191 A149192 this_sequence A149193 A149194 
               A149195
%Y A032123 Adjacent sequences: A032120 A032121 A032122 this_sequence A032124 A032125 
               A032126
%K A032123 nonn
%O A032123 0,3
%A A032123 Christian G. Bower (bowerc(AT)usa.net)