Number of permutations p of [n] such that p(i) > p(i+1) iff i == 1 (mod 7).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =4a(6) =5a(7) =6a(8) =7a(9) =55a(10) =306a(11) =1145a(12) =3454a(13) =8997a(14) =21008a(15) =45031a(16) =630421a(17) =5954062a(18) =36439007a(19) =174011100a(20) =697278853a(21) =2442137774a(22) =7677528495a(23) =154507257827