a(n) = T(n,0) + T(n,1) + ... + T(n,n), T given by A026536.

Terms

a(0) =1a(1) =1a(2) =4a(3) =7a(4) =22a(5) =42a(6) =127a(7) =249a(8) =746a(9) =1476a(10) =4414a(11) =8766a(12) =26215a(13) =52158a(14) =156041a(15) =310799a(16) =930194a(17) =1854072a(18) =5550976a(19) =11070000a(20) =33152042a(21) =66139316a(22) =198115526a(23) =395368914a(24) =1184511095a(25) =2364457980a(26) =7084871668a(27) =14145343660a(28) =42390336619