Expansion of 1/(1+4*x*c(x)), c(x) the g.f. of Catalan numbers A000108.

Terms

a(0) =1a(1) =-4a(2) =12a(3) =-40a(4) =124a(5) =-408a(6) =1272a(7) =-4176a(8) =13020a(9) =-42808a(10) =133096a(11) =-439344a(12) =1358872a(13) =-4514800a(14) =13853040a(15) =-46469280a(16) =140945820a(17) =-479312760a(18) =1430085000a(19) =-4958382960a(20) =14453014920a(21) =-51500944080a(22) =145230007440a(23) =-537922074720