Expansion of (1-x-sqrt(1-6x-3x^2))/(2x).

Terms

a(0) =1a(1) =3a(2) =9a(3) =36a(4) =162a(5) =783a(6) =3969a(7) =20817a(8) =112023a(9) =615033a(10) =3431403a(11) =19398690a(12) =110880900a(13) =639730305a(14) =3720657807a(15) =21790419444a(16) =128398625658a(17) =760668489729