a(n) is the number of semi-meanders with n top arches that have at least one arch with length 1 adjacent to the center of the top arch configuration or at either end of the arch configuration.
A333971
a(n) is the number of semi-meanders with n top arches that have at least one arch with length 1 adjacent to the center of the top arch configuration or at either end of the arch configuration.
Terms
- a(0) =1a(1) =2a(2) =4a(3) =8a(4) =24a(5) =56a(6) =168a(7) =432a(8) =1320a(9) =3608a(10) =11216a(11) =31952a(12) =100720a(13) =295600a(14) =942272a(15) =2828112a(16) =9097256a(17) =27785112a(18) =90048656a(19) =278899152a(20) =909566560a(21) =2849498656a(22) =9342566152a(23) =29548420688a(24) =97323261664
External references
- oeis: A333971