Expansion of 2/(1 + 2*x + sqrt(1 - 4*x*(1 + x))).

Terms

a(0) =1a(1) =0a(2) =2a(3) =4a(4) =16a(5) =56a(6) =216a(7) =848a(8) =3424a(9) =14080a(10) =58816a(11) =248832a(12) =1064064a(13) =4591744a(14) =19970432a(15) =87448832a(16) =385226240a(17) =1705979904a(18) =7590632448a(19) =33916934144a(20) =152128126976a(21) =684702330880