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

Terms

a(0) =1a(1) =2a(2) =-2a(3) =6a(4) =-22a(5) =90a(6) =-394a(7) =1806a(8) =-8558a(9) =41586a(10) =-206098a(11) =1037718a(12) =-5293446a(13) =27297738a(14) =-142078746a(15) =745387038a(16) =-3937603038a(17) =20927156706a(18) =-111818026018a(19) =600318853926