A005319 and A002315 interleaved.

Terms

a(0) =0a(1) =1a(2) =4a(3) =7a(4) =24a(5) =41a(6) =140a(7) =239a(8) =816a(9) =1393a(10) =4756a(11) =8119a(12) =27720a(13) =47321a(14) =161564a(15) =275807a(16) =941664a(17) =1607521a(18) =5488420a(19) =9369319a(20) =31988856a(21) =54608393a(22) =186444716a(23) =318281039a(24) =1086679440a(25) =1855077841a(26) =6333631924a(27) =10812186007a(28) =36915112104a(29) =63018038201