A081698 Expansion of ( 1 - Sqrt[ 1 - 4 x Sqrt[ 1 + 4 x ] ] )/( 2 x ).

1, 3, 4, 21, 56, 282, 984, 4813, 19280, 93150, 403672, 1945954, 8845360, 42766292, 200419504, 974134461, 4659558048, 22785183670, 110564976792, 543935554390, 2667398588272, 13196971915628, 65238895435792, 324431740601618