a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, s(1) = 1, s(n) = 3, |s(i) - s(i-1)| <= 1 for i >= 2, |s(2) - s(1)| = 1, |s(3) - s(2)| = 1 if s(2) = 1. Also a(n) = T(n,n-3), where T is the array in A026268.
A026289
a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, s(1) = 1, s(n) = 3, |s(i) - s(i-1)| <= 1 for i >= 2, |s(2) - s(1)| = 1, |s(3) - s(2)| = 1 if s(2) = 1. Also a(n) = T(n,n-3), where T is the array in A026268.
Terms
- a(0) =1a(1) =3a(2) =9a(3) =27a(4) =79a(5) =229a(6) =659a(7) =1889a(8) =5402a(9) =15430a(10) =44054a(11) =125786a(12) =359296a(13) =1026936a(14) =2937444a(15) =8409540a(16) =24097737a(17) =69118635a(18) =198442329a(19) =570286939a(20) =1640469427a(21) =4723363073a(22) =13612376671a(23) =39265012213a(24) =113358893147a(25) =327545797361a(26) =947203621523
External references
- oeis: A026289