a(n) = A036765(n-1) if n>0, with a(0) = 1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =13a(6) =36a(7) =104a(8) =309a(9) =939a(10) =2905a(11) =9118a(12) =28964a(13) =92940a(14) =300808a(15) =980864a(16) =3219205a(17) =10626023a(18) =35252867a(19) =117485454a(20) =393133485a(21) =1320357501a(22) =4449298136a(23) =15038769672a(24) =50973266380a(25) =173214422068a(26) =589998043276