Sum{T(i,j)}, 0<=i<=n, 0<=j<=n, T given by A026659.

Terms

a(0) =1a(1) =3a(2) =7a(3) =17a(4) =37a(5) =79a(6) =163a(7) =359a(8) =751a(9) =1593a(10) =3277a(11) =7155a(12) =14911a(13) =31697a(14) =65269a(15) =142115a(16) =295807a(17) =629805a(18) =1297801a(19) =2821249a(20) =5868145a(21) =12507295a(22) =25785595a(23) =55992063a(24) =116404999a(25) =248297225a(26) =512081677a(27) =1111033773a(28) =2308937965