Number of Dyck n-paths with equally spaced returns.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =7a(5) =15a(6) =48a(7) =133a(8) =456a(9) =1439a(10) =5060a(11) =16797a(12) =60693a(13) =208013a(14) =760326a(15) =2677217a(16) =9879513a(17) =35357671a(18) =131763844a(19) =477638701a(20) =1790943777a(21) =6566420517a(22) =24748372638a(23) =91482563641a(24) =346597488614