a(n) = p(n+3)-p(n+1), where p(n) = A238825(n).

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =22a(5) =53a(6) =131a(7) =323a(8) =798a(9) =1968a(10) =4853a(11) =11958a(12) =29463a(13) =72581a(14) =178803a(15) =440474a(16) =1085110a(17) =2673183a(18) =6585468a(19) =16223521a(20) =39967243a(21) =98460769a(22) =242561730a(23) =597559646a(24) =1472109847a(25) =3626595728a(26) =8934249307a(27) =22009844973a(28) =54222045921a(29) =133577963318