%I A129815
%S A129815 0,0,1,2,6,22,102,506,2952,18502,131112,991226,8271792,73176262,
%T A129815 703077552,7121578106,77437418112,883521487942,10726837356672,
%U A129815 136104948161786
%N A129815 Number of reverse alternating fixed-point-free permutations on n letters.
%C A129815 Contribution from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 06 2009: 
               (Start)
%C A129815 Reverse alternating permutations are called also up-down permutations.
%C A129815 a(n) is also the number of reverse alternating permutations having exactly 
               1 fixed point (see the Stanley reference). Example: a(4)=2 because 
               we have 1423 and 2314.
%C A129815 a(2n-1)=A129817(2n-1)
%C A129815 (End)
%H A129815 R. P. Stanley, <a href="http://arXiv.org/abs/math.CO/0603520">Alternating 
               permutations and symmetric functions</a>
%e A129815 Contribution from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 06 2009: 
               (Start)
%e A129815 a(4)=2 because we have 3412 and 2413.
%e A129815 (End)
%Y A129815 Cf. A000111, A000166, A007779.
%Y A129815 Sequence in context: A002772 A000140 A079263 this_sequence A103941 A064643 
               A129535
%Y A129815 Adjacent sequences: A129812 A129813 A129814 this_sequence A129816 A129817 
               A129818
%K A129815 more,nonn
%O A129815 1,4
%A A129815 Vladeta Jovovic (vladeta(AT)eunet.rs), May 20 2007