A242839 - OEIS

%I #5 May 24 2014 18:25:14

%S 2,0,5,0,14,0,22,24,104,228,518,1272,2621,5986,11836,25396,49077,

%T 100200,192678,381724,730806,1424956,2727666,5271456,10111091,

%U 19503830,37551786,72600610,140531739,273027876,531953163,1040051736,2040532257,4017104634,7935847124

%N Number of compositions of n with difference -2 between the number of odd parts and the number of even parts, both counted without multiplicity.

%H Alois P. Heinz, <a href="/A242839/b242839.txt">Table of n, a(n) for n = 6..500</a>

%e a(6) = 2: [2,4], [4,2].

%e a(8) = 5: [2,2,4], [2,4,2], [4,2,2], [2,6], [6,2].

%e a(13) = 24 = 4!: all permutations of {1,2,4,6}.

%Y Column k=-2 of A242626.

%K nonn

%O 6,1

%A _Alois P. Heinz_, May 23 2014