Search: id:A007481
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%I A007481 M0828
%S A007481 1,2,3,7,11,25,39,89,139,317,495,1129,1763,4021,6279,14321,22363,51005,
%T A007481 79647,181657,283667,646981,1010295,2304257,3598219,8206733,12815247,
%U A007481 29228713,45642179,104099605,162557031,370756241,578955451,1320467933
%N A007481 Number of subsequences of [ 1,...,n ] in which each even number has an 
               odd neighbor.
%D A007481 R. K. Guy and W. O. J. Moser, Numbers of subsequences without isolated 
               odd members. Fibonacci Quarterly, 34, No. 2, 152-155 (1996).
%D A007481 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A007481 T. D. Noe, <a href="b007481.txt">Table of n, a(n) for n=0..400</a>
%F A007481 a(n) = 3*a(n-2) + 2*a(n-4).
%e A007481 For n=2, there are the following three subsequences of [1,2] with the 
               desired property: empty, [1], [1,2].
%e A007481 For n=3, there are the following seven subsequences of [1,2,3] with the 
               desired property: empty, [1], [3], [1,2], [2,3], [1,3], [1,2,3].
%Y A007481 Cf. A007455, A007482, A007484.
%Y A007481 Sequence in context: A129940 A128631 A092217 this_sequence A121268 A101173 
               A005246
%Y A007481 Adjacent sequences: A007478 A007479 A007480 this_sequence A007482 A007483 
               A007484
%K A007481 nonn,easy,nice
%O A007481 0,2
%A A007481 N. J. A. Sloane (njas(AT)research.att.com).
%E A007481 More terms from James A. Sellers (sellersj(AT)math.psu.edu), Dec 24 1999

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