Avoiding the pattern 121'2'. To avoid 121'2' means not to have four consecutive letters such that the first letter is less than the second one and the third letter is less than the fourth one.
A177471
Avoiding the pattern 121'2'. To avoid 121'2' means not to have four consecutive letters such that the first letter is less than the second one and the third letter is less than the fourth one.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =18a(5) =61a(6) =281a(7) =1541a(8) =8920a(9) =57924a(10) =437490a(11) =3611389a(12) =31721537a(13) =304085783a(14) =3180772870a(15) =35422074330a(16) =418050879810
External references
- oeis: A177471