Number of permutations of 1..n avoiding adjacent step pattern up, down, up, up.
A177521
Number of permutations of 1..n avoiding adjacent step pattern up, down, up, up.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =111a(6) =612a(7) =3906a(8) =28701a(9) =236527a(10) =2167862a(11) =21824925a(12) =239861934a(13) =2854894485a(14) =36602472117a(15) =502718236303
External references
- oeis: A177521