The z^2 coefficients of the polynomials in the GF1 denominators of A156921.

Terms

a(0) =7a(1) =75a(2) =385a(3) =1365a(4) =3850a(5) =9282a(6) =19950a(7) =39270a(8) =72105a(9) =125125a(10) =207207a(11) =329875a(12) =507780a(13) =759220a(14) =1106700a(15) =1577532a(16) =2204475a(17) =3026415a(18) =4089085a(19) =5445825a(20) =7158382a(21) =9297750a(22) =11945050a(23) =15192450a(24) =19144125a(25) =23917257