G.f.: (1-2*x*c(x))/(1-3*x*c(x)) where c(x) = (1 - sqrt(1-4*x))/(2*x) is the g.f. for Catalan numbers A000108.
A049027
G.f.: (1-2*x*c(x))/(1-3*x*c(x)) where c(x) = (1 - sqrt(1-4*x))/(2*x) is the g.f. for Catalan numbers A000108.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =17a(4) =74a(5) =326a(6) =1446a(7) =6441a(8) =28770a(9) =128750a(10) =576944a(11) =2587850a(12) =11615932a(13) =52167688a(14) =234383146a(15) =1053386937a(16) =4735393794a(17) =21291593238a(18) =95747347176a(19) =430624242942
External references
- oeis: A049027