%I A121285
%S A121285 1,1,2,4,10,22,54,120,284,626,1438,3136,7044,15212,33596,71952,156856,
               333610,
%T A121285 719886,1522224,3257972,6855476,14574772,30541264,64571400,134827252,283727564,
%U A121285 590608960,1237926184,2569953496,5368225848,11118205088,23155034480,47856472218
%N A121285 a(0) = 1; for n>0, a(n) = (n+3)*2^(n-2)-n*binomial(n-1, floor( (n-1)/
               2 ))-(n-1)*binomial(n-2,floor((n-2)/2)).
%D A121285 A. Bernini, F. Disanto, R. Pinzani and S. Rinaldi, Permutations defining 
               convex permutominoes, preprint, 2007. [See S_{n+1}.]
%Y A121285 Sequence in context: A075560 A078040 A164990 this_sequence A030234 A148086 
               A076875
%Y A121285 Adjacent sequences: A121282 A121283 A121284 this_sequence A121286 A121287 
               A121288
%K A121285 nonn
%O A121285 0,3
%A A121285 N. J. A. Sloane (njas(AT)research.att.com), Jul 28 2007