a(n) = number of (s(0), s(1), ..., s(n)) such that s(i) is an integer, s(0) = 0, |s(1)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2, s(n) = 2. Also a(n) = T(n,n-2), where T is the array defined in A025177.
A025180
a(n) = number of (s(0), s(1), ..., s(n)) such that s(i) is an integer, s(0) = 0, |s(1)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2, s(n) = 2. Also a(n) = T(n,n-2), where T is the array defined in A025177.
Terms
- a(0) =1a(1) =2a(2) =7a(3) =20a(4) =60a(5) =176a(6) =518a(7) =1520a(8) =4461a(9) =13090a(10) =38423a(11) =112828a(12) =331487a(13) =974442a(14) =2866125a(15) =8434992a(16) =24838275a(17) =73181142a(18) =215729781a(19) =636275820a(20) =1877569134a(21) =5543095404a(22) =16372140876a(23) =48377825216a(24) =143009973875a(25) =422918975726
External references
- oeis: A025180