**Define an array as follows: b(i,0)=b(0,j)=1, b(i,j)=2*b(i-1,j-1)+b(i-1,j)+b(i,j-1). Then a(n)=b(n,n).**

*1, 4, 22, 136, 886, 5944, 40636, 281488, 1968934, 13875544, 98365972, 700701808*

*1 seqfan posts*

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

Links to OEIS content are included according to The OEIS End-User License Agreement .