%I A124400
%S A124400 1,1,4,7,18,38,88,195,441,988,2223,4992,11220,25208,56645,127277,285992,
%T A124400 642615,1443946,3244514,7290360,16381287,36808421,82707768,185842671,
%U A124400 417584688,938304280,2108350576,4737420745,10644887785,23918845740
%N A124400 a(0)=1, a(1)=1, a(2)=4, a(3)=7, a(n)=a(n-1)+3*a(n-2)-a(n-4) for n>=4.
%C A124400 Unsigned version of A077920.
%F A124400 G.f.: 1/(1-x-3*x^2+x^4).
%Y A124400 Sequence in context: A056318 A011948 A146387 this_sequence A077920 A135582 
               A100828
%Y A124400 Adjacent sequences: A124397 A124398 A124399 this_sequence A124401 A124402 
               A124403
%K A124400 easy,nonn
%O A124400 0,3
%A A124400 Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Dec 14 2006