The number of partitions of [n] with exactly 4 blocks without peaks.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =4a(5) =16a(6) =64a(7) =236a(8) =818a(9) =2736a(10) =8934a(11) =28622a(12) =90324a(13) =281792a(14) =871556a(15) =2677750a(16) =8184383a(17) =24913238a(18) =75593383a(19) =228793147a(20) =691094857a(21) =2084237036a(22) =6277871658a(23) =18890568921a(24) =56798001639a(25) =170665733660a(26) =512554832309