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

*0, 1, 3, 12, 45, 171, 648, 2457, 9315, 35316, 133893, 507627, 1924560, 7296561*

*2 seqfan posts*

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

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