a(n) is the total number of paths starting at (0, 0), ending at (n, 0), consisting of steps (1, 1), (1, 0), (1, -2), and staying on or above y = -2.
A378850
a(n) is the total number of paths starting at (0, 0), ending at (n, 0), consisting of steps (1, 1), (1, 0), (1, -2), and staying on or above y = -2.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =4a(4) =13a(5) =31a(6) =73a(7) =190a(8) =505a(9) =1316a(10) =3431a(11) =9065a(12) =24122a(13) =64325a(14) =172082a(15) =462344a(16) =1246685a(17) =3371135a(18) =9140289a(19) =24847422a(20) =67708743a(21) =184906614a(22) =505986933a(23) =1387240401a(24) =3810083424a(25) =10481797131a(26) =28880894706a(27) =79692785251a(28) =220203155689a(29) =609242057143
External references
- oeis: A378850