a(n) = T(n,0) + T(n,1) + ... + T(n,n), T given by A026519.

Terms

a(0) =1a(1) =2a(2) =4a(3) =11a(4) =22a(5) =64a(6) =127a(7) =376a(8) =746a(9) =2222a(10) =4414a(11) =13180a(12) =26215a(13) =78373a(14) =156041a(15) =466840a(16) =930194a(17) =2784266a(18) =5550976a(19) =16620976a(20) =33152042a(21) =99291358a(22) =198115526a(23) =593484440a(24) =1184511095a(25) =3548969075a(26) =7084871668a(27) =21230215328a(28) =42390336619