Leading diagonal of triangle in A080521.

Terms

a(0) =1a(1) =3a(2) =5a(3) =10a(4) =22a(5) =49a(6) =107a(7) =228a(8) =476a(9) =979a(10) =1993a(11) =4030a(12) =8114a(13) =16293a(14) =32663a(15) =65416a(16) =130936a(17) =261991a(18) =524117a(19) =1048386a(20) =2096942a(21) =4194073a(22) =8388355a(23) =16776940a(24) =33554132a(25) =67108539a(26) =134217377a(27) =268435078a(28) =536870506a(29) =1073741389