Number of permutations p of [n] such that p(i), p(i+3), p(i+6),... form an up-down sequence for i in {1,2,3}.
A367336
Number of permutations p of [n] such that p(i), p(i+3), p(i+6),... form an up-down sequence for i in {1,2,3}.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =12a(5) =30a(6) =90a(7) =420a(8) =2240a(9) =13440a(10) =84000a(11) =577500a(12) =4331250a(13) =36036000a(14) =322882560a(15) =3099672576a(16) =31513337856a(17) =340409701632
External references
- oeis: A367336