Search: id:A000486
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%I A000486 M5011 N2158
%S A000486 16,150,926,4788,22548,100530,433162,1825296,7577120,31130190,126969558,
%T A000486 515183724,2082553132,8395437930,33776903714,135691891272,544517772984,
%U A000486 2183315948550,8748985781230,35043081823140,140313684667076
%N A000486 One half of the number of permutations of [n] such that the differences 
               have 4 runs with the same signs.
%D A000486 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A000486 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A000486 F. N. David, M. G. Kendall and D. E. Barton, Symmetric Function and Allied 
               Tables, Cambridge, 1966, p. 260.
%D A000486 L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 260, #13
%F A000486 8*a(n)/4^n ->1 as n ->infinity . - DELEHAM Philippe (kolotoko(AT)wanadoo.fr), 
               Feb 22 2004
%e A000486 a(5)=16 because the permutations of [5] with four sign runs are 13254, 
               14253, 14352, 15342, 15243, 21435, 21534, 23154, 24153, 25143, 31425, 
               31524, 32415, 32514, 41325, 42315 and their reversals.
%Y A000486 a(n)=T(n, 4), where T(n, k) is the array defined in A008970.
%Y A000486 Equals 1/2 * A060158(n).
%Y A000486 Sequence in context: A126537 A155657 A135458 this_sequence A006420 A049351 
               A023014
%Y A000486 Adjacent sequences: A000483 A000484 A000485 this_sequence A000487 A000488 
               A000489
%K A000486 nonn
%O A000486 5,1
%A A000486 N. J. A. Sloane (njas(AT)research.att.com).
%E A000486 Edited by Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 18 2004

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