Search: id:A000382
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%I A000382 M4087 N1696
%S A000382 6,11,20,36,65,119,218,400,735,1351,2484,4568,8401,15451,28418,
%T A000382 52268,96135,176819,325220,598172,1100209,2023599,3721978,6845784
%N A000382 Restricted permutations.
%D A000382 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A000382 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A000382 S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques 
               Conjectures, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 
               1992.
%D A000382 N. S. Mendelsohn, Permutations with restricted displacement, Canad. Math. 
               Bull., 4 (1961), 29-38.
%H A000382 S. Plouffe, <a href="http://www.lacim.uqam.ca/%7Eplouffe/articles/MasterThesis.pdf">
               Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures</
               a>, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 
               1992.
%H A000382 S. Plouffe, <a href="http://www.lacim.uqam.ca/%7Eplouffe/articles/FonctionsGeneratrices.pdf">
               1031 Generating Functions and Conjectures</a>, Universit\'{e} du 
               Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
%F A000382 a(n) = a(n-1)+a(n-2)+a(n-3)-2 (conjectured).
%p A000382 A000382:=-(-6+z+2*z**2+4*z**3+z**4)/(z-1)/(z**3+z**2+z-1); [Conjectured 
               by S. Plouffe in his 1992 dissertation.]
%p A000382 a:= n-> if n<4 then 0 elif n=4 then 6 else (Matrix([[11,7,4,2]]). Matrix(4, 
               (i,j)-> if (i=j-1) then 1 elif j=1 then [2,0,0,-1][i] else 0 fi)^(n-2))[1,
               4] fi: seq (a(n), n=4..27); [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), 
               Aug 26 2008]
%Y A000382 Cf. A000496, A020992.
%Y A000382 Sequence in context: A160842 A007745 A021011 this_sequence A000383 A083575 
               A046616
%Y A000382 Adjacent sequences: A000379 A000380 A000381 this_sequence A000383 A000384 
               A000385
%K A000382 nonn
%O A000382 4,1
%A A000382 N. J. A. Sloane (njas(AT)research.att.com).

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