Complement of A381767.

Terms

a(0) =2a(1) =3a(2) =5a(3) =15a(4) =46a(5) =136a(6) =385a(7) =1072a(8) =2949a(9) =8063a(10) =21977a(11) =59814a(12) =162683a(13) =442329a(14) =1202507a(15) =3268905a(16) =8885983a(17) =24154809a(18) =65659808a(19) =178482121a(20) =485164996a(21) =1318815514a(22) =3584912605a(23) =9744803182a(24) =26489121842a(25) =72004899025a(26) =195729609091a(27) =532048240238