a(0) = 0, a(1) = 1, a(2*n) = n*a(2*n-1) + a(2*n-2), a(2*n+1) = a(2*n) + a(2*n-1).

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =5a(5) =7a(6) =26a(7) =33a(8) =158a(9) =191a(10) =1113a(11) =1304a(12) =8937a(13) =10241a(14) =80624a(15) =90865a(16) =807544a(17) =898409a(18) =8893225a(19) =9791634a(20) =106809565a(21) =116601199a(22) =1389422754a(23) =1506023953a(24) =19461710190a(25) =20967734143a(26) =292042254049a(27) =313009988192