Main diagonal of arrays A265901 and A265903.

Terms

a(0) =1a(1) =7a(2) =27a(3) =62a(4) =227a(5) =496a(6) =1013a(7) =2045a(8) =7893a(9) =16226a(10) =32650a(11) =65414a(12) =131026a(13) =262109a(14) =524267a(15) =1048572