Search: id:A129815 Results 1-1 of 1 results found. %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, Alternating permutations and symmetric functions %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 Search completed in 0.001 seconds