Main diagonal of square array A145153.

Terms

a(0) =0a(1) =1a(2) =2a(3) =6a(4) =20a(5) =71a(6) =259a(7) =960a(8) =3597a(9) =13586a(10) =51635a(11) =197223a(12) =756380a(13) =2910707a(14) =11233311a(15) =43460144a(16) =168502849a(17) =654547456a(18) =2546819347a(19) =9924285801a(20) =38723794820a(21) =151278566731a(22) =591628491483