Expansion of 1/sqrt(1 - 6x + 21x^2).

Terms

a(0) =1a(1) =3a(2) =3a(3) =-27a(4) =-189a(5) =-567a(6) =189a(7) =11259a(8) =59859a(9) =129033a(10) =-395847a(11) =-4730481a(12) =-19580211a(13) =-21264201a(14) =258785523a(15) =1917734373a(16) =6051991059a(17) =-2659507911a(18) =-135544952151a(19) =-738957668337