Coefficient of x in the reduction by x^2 -> x+1 of the polynomial p(n,x) defined at Comments.

Terms

a(0) =0a(1) =1a(2) =3a(3) =9a(4) =20a(5) =40a(6) =74a(7) =131a(8) =225a(9) =379a(10) =630a(11) =1038a(12) =1700a(13) =2773a(14) =4511a(15) =7325a(16) =11880a(17) =19252a(18) =31182a(19) =50487a(20) =81725a(21) =132271a(22) =214058a(23) =346394a(24) =560520a(25) =906985a(26) =1467579a(27) =2374641a(28) =3842300a(29) =6217024