G.f. A(x) satisfies A(x) = 1 + x*A(x)*abs( 1/A(x)^2 ).

Terms

a(0) =1a(1) =1a(2) =3a(3) =8a(4) =19a(5) =52a(6) =130a(7) =350a(8) =887a(9) =2386a(10) =6178a(11) =16318a(12) =42618a(13) =112632a(14) =295072a(15) =777628a(16) =2039543a(17) =5379446a(18) =14139050a(19) =37212510a(20) =97869194a(21) =257724328a(22) =677880176a(23) =1784741604a(24) =4694887026a(25) =12362045980a(26) =32529481476a(27) =85628088892a(28) =225332403940a(29) =593217232816