Main diagonal of triangle A131791: a(n) = A131791(n,n) for n>=0.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =76a(6) =280a(7) =1045a(8) =3936a(9) =14925a(10) =56892a(11) =217791a(12) =836706a(13) =3224157a(14) =12456225a(15) =48232162a(16) =187131664a(17) =727309265a(18) =2831193004a(19) =11036424667a(20) =43076087806a(21) =168322335246a(22) =658416150496