Number of double rises at an even level in all nondecreasing Dyck paths of semilength n. A nondecreasing Dyck path is a Dyck path for which the sequence of the altitudes of the valleys is nondecreasing.
A121532
Number of double rises at an even level in all nondecreasing Dyck paths of semilength n. A nondecreasing Dyck path is a Dyck path for which the sequence of the altitudes of the valleys is nondecreasing.
Terms
- a(0) =0a(1) =0a(2) =1a(3) =6a(4) =24a(5) =87a(6) =290a(7) =926a(8) =2861a(9) =8640a(10) =25634a(11) =75015a(12) =217100a(13) =622620a(14) =1772097a(15) =5011394a(16) =14093980a(17) =39448623a(18) =109954398a(19) =305344314a(20) =845165725a(21) =2332485420a(22) =6420202246a(23) =17629525871a(24) =48304680504a(25) =132092031672a(26) =360557665825
External references
- oeis: A121532