A242821 - OEIS

%I #9 May 24 2014 18:00:49

%S 1,0,0,2,3,11,14,33,43,82,141,260,514,1049,2321,4789,10454,21735,

%T 46213,94782,196060,398662,810178,1631089,3278372,6556096,13088339,

%U 26063238,51824061,102926784,204239173,405087125,803109813,1592179369,3156298826,6258390137

%N Number of compositions of n with equal number of even and odd parts, both counted without multiplicity.

%H Alois P. Heinz, <a href="/A242821/b242821.txt">Table of n, a(n) for n = 0..500</a>

%e a(3) = 2: [1,2], [2,1].

%e a(4) = 3: [1,1,2], [1,2,1], [2,1,1].

%e a(5) = 11: [1,1,1,2], [1,1,2,1], [1,2,1,1], [2,1,1,1], [1,2,2], [2,1,2], [2,2,1], [2,3], [3,2], [1,4], [4,1].

%e a(6) = 14: [1,1,1,1,2], [1,1,1,2,1], [1,1,2,1,1], [1,2,1,1,1], [2,1,1,1,1], [1,1,2,2], [1,2,1,2], [1,2,2,1], [2,1,1,2], [2,1,2,1], [2,2,1,1], [1,1,4], [1,4,1], [4,1,1].

%Y Column k=0 of A242626.

%Y Cf. A098123 (counted with multiplicity).

%K nonn

%O 0,4

%A _Alois P. Heinz_, May 23 2014