a(n) = A027082(n, 2n-8).

Terms

a(0) =1a(1) =1a(2) =5a(3) =17a(4) =57a(5) =193a(6) =650a(7) =2173a(8) =7199a(9) =23619a(10) =76746a(11) =247103a(12) =788934a(13) =2499707a(14) =7866233a(15) =24603551a(16) =76538239a(17) =236960031a(18) =730506849a(19) =2243545795a(20) =6867375720a(21) =20958167581a(22) =63791696431a(23) =193708118293a(24) =586967142587