Main diagonal of number square A081206.

Terms

a(0) =1a(1) =2a(2) =3a(3) =7a(4) =16a(5) =37a(6) =89a(7) =216a(8) =529a(9) =1307a(10) =3248a(11) =8111a(12) =20339a(13) =51176a(14) =129143a(15) =326717a(16) =828374a(17) =2104361a(18) =5354979a(19) =13647682a(20) =34830191a(21) =89000157a(22) =227674188a(23) =583017657a(24) =1494365341a(25) =3833592212a(26) =9842373849a(27) =25287895051a(28) =65016153154a(29) =167264946727