Search: id:A005656
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%I A005656 M2920
%S A005656 0,0,1,3,12,44,170,651,2520,9752,37854,147070,572264,2229096,
%T A005656 8692788,33933459,132594480,518584880,2029976630,7952706234,
%U A005656 31179618184,122331419080,480283635468,1886828198398
%N A005656 Number of bracelets (turn over necklaces) with n red, 1 pink and n-3 
               blue beads; also reversible strings with n red and n-3 blue beads.
%D A005656 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005656 Ascher, Marcia; Mu torere: an analysis of a Maori game. Math. Mag. 60 
               (1987), no. 2, 90-100.
%H A005656 <a href="Sindx_Br.html#bracelets">Index entries for sequences related 
               to bracelets</a>
%H A005656 F. Ruskey, <a href="http://www.theory.cs.uvic.ca/~cos/inf/neck/NecklaceInfo.html">
               Necklaces, Lyndon words, De Bruijn sequences, etc.</a>
%F A005656 a(n)= (1/2) (C(2n-3, n-3)+C(n-2, [ (n-3)/2 ])).
%o A005656 (PARI) a(n)= (1/2) *(C(2*n-3,n-3)+C(n-2,(n-3)\2)) where C(n,k)= if(k<0|k>
               n,0,n!/k!/(n-k)!)
%Y A005656 A005656(n)=A034851(2n-3, n-3)
%Y A005656 Sequence in context: A012873 A167477 A109437 this_sequence A064017 A005320 
               A062561
%Y A005656 Adjacent sequences: A005653 A005654 A005655 this_sequence A005657 A005658 
               A005659
%K A005656 nonn
%O A005656 1,4
%A A005656 N. J. A. Sloane (njas(AT)research.att.com).
%E A005656 Sequence corrected, extended and description corrected by Christian G. 
               Bower (bowerc(AT)usa.net). Formula from Michael Somos.

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