A200047 - OEIS

%I #6 Mar 30 2012 17:37:36

%S 0,1,0,1,2,3,5,9,15,25,42,70,116,192,317,522,858,1408,2307,3775,6170,

%T 10074,16433,26784,43623,71002,115497,187777,305147,495669,804839,

%U 1306404,2119884,3438952,5577396,9043549,14660810,23762784,38509220,62397495,101090631

%N Number of compositions of n having smallest part equal to 2.

%H Alois P. Heinz, <a href="/A200047/b200047.txt">Table of n, a(n) for n = 1..1000</a>

%F G.f.: (x-1)^2*x^2/(1-2*x+x^4+x^5).

%e a(7) = 5: [2,2,3], [2,3,2], [2,5], [3,2,2], [5,2].

%p a:= n-> (<<0|1|0|0|0>, <0|0|1|0|0>, <0|0|0|1|0>, <0|0|0|0|1>, <-1|-1|0|0|2>>^n. <<0, 0, 1, 0, 1>>)[1, 1]: seq (a(n), n=1..50);

%Y Column k=2 of A105147.

%K nonn

%O 1,5

%A _Alois P. Heinz_, Nov 13 2011