Number of permutations p of [n] such that p(i) > p(i+1) iff i == 1 (mod 10).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =4a(6) =5a(7) =6a(8) =7a(9) =8a(10) =9a(11) =10a(12) =109a(13) =768a(14) =3627a(15) =13636a(16) =43665a(17) =123744a(18) =318223a(19) =755802a(20) =1679581a(21) =3527140a(22) =70542781a(23) =878845662a(24) =7113969943a(25) =44573747024a(26) =231938007625