Search: id:A051437
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%I A051437
%S A051437 1,3,4,10,16,36,64,136,256,528,1024,2080,4096,8256,16384,32896,65536,
%T A051437 131328,262144,524800,1048576,2098176,4194304,8390656,16777216,
%U A051437 33558528
%N A051437 Undirected walks of length n+1 on an oriented triangle, visiting n+2 
               vertices, with n "corners"; the symmetry group is C3. Walks are not 
               self-avoiding.
%F A051437 n=2m: a(n)=2^(n-1)+2^((n-2)/2); n=2m+1: a(n)=2^(n-1).
%F A051437 Binomial transform is 3^n+Pell(n) (A000244(n)+A000129(n)). G.f. : (1+x-4x^2)/
               ((1-2x)(1-2x^2)); a(n)=2^n+2^(n/2)(1-(-1)^n)/(2sqrt(2)). - Paul Barry 
               (pbarry(AT)wit.ie), Apr 28 2004
%e A051437 For n=3 the walks visit vertices 1212, 1213, 1232, 1231.
%Y A051437 Cf. A005418.
%Y A051437 Sequence in context: A037952 A093512 A081160 this_sequence A034774 A144958 
               A034775
%Y A051437 Adjacent sequences: A051434 A051435 A051436 this_sequence A051438 A051439 
               A051440
%K A051437 nonn,nice,easy
%O A051437 0,2
%A A051437 Colin Mallows colinm(AT)research.avayalabs.com

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