**a(0)=0,a(1)=1,a(2)=2,a(3)=5 then a(n+4)=2a(n+3)+2a(n+2)+2a(n+1)-a(n).**

*0, 1, 2, 5, 16, 45, 130, 377, 1088, 3145, 9090, 26269, 75920, 219413, 634114*

*3 seqfan posts*

Index of A-numbers in seqfan: by ascending order by month by frequency by keyword

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