Column 3 of A052250.

Terms

a(0) =1a(1) =3a(2) =6a(3) =13a(4) =27a(5) =63a(6) =148a(7) =363a(8) =912a(9) =2330a(10) =6036a(11) =15825a(12) =41865a(13) =111636a(14) =299736a(15) =809513a(16) =2197728a(17) =5994219a(18) =16416748a(19) =45129396a(20) =124479270a(21) =344403494a(22) =955557780a(23) =2658061560a(24) =7411457963a(25) =20710700277a(26) =57992124810a(27) =162691293718a(28) =457219737027