Expansion of (1-sqrt(1-4*x-20*x^2))/(2*x).

Terms

a(0) =1a(1) =6a(2) =12a(3) =60a(4) =264a(5) =1392a(6) =7392a(7) =41424a(8) =236640a(9) =1384512a(10) =8224896a(11) =49554816a(12) =301884672a(13) =1856878080a(14) =11514915840a(15) =71915838720a(16) =451938731520