Principal diagonal of the convolution array A213568.

Terms

a(0) =1a(1) =7a(2) =25a(3) =71a(4) =181a(5) =435a(6) =1009a(7) =2287a(8) =5101a(9) =11243a(10) =24553a(11) =53223a(12) =114661a(13) =245731a(14) =524257a(15) =1114079a(16) =2359261a(17) =4980699a(18) =10485721a(19) =22020055a(20) =46137301a(21) =96468947a(22) =201326545a(23) =419430351a(24) =872415181a(25) =1811939275a(26) =3758096329a(27) =7784628167a(28) =16106127301a(29) =33285996483