{"kind":"theorem_check","report":{"conclusion":{"first_index":1,"simple_roots":false,"statement":"every P_n, n >= 1, is nonzero and real-rooted; for n >= 2, Q_(n-1) interlaces Q_n (weakly, in the sense of Liu and Wang; no interlacing of the P_n is claimed)"},"hypotheses":[{"evidence":"degrees 0 and 1; real-rooted and Q_1 << Q_2 checked exactly","name":"seed_rows","statement":"Q_1 and Q_2 are nonzero and real-rooted, of degrees e and e or e + 1, and Q_1 << Q_2 (weak interlacing)","status":{"kind":"verified"}},{"evidence":"l_n = ([x^1] A_n) l_(n-1) + ([x^2] B_n) l_(n-2) when deg P_(n-1) - deg P_(n-2) = 1 (then deg P_n - deg P_(n-1) = 1): positive-ratio induction with g(n) = (n)/(n - 1) (the exact ratio): g(n) > 0 for every integer n in [3, +inf) (exact; Taylor shift: the coefficients of g(n) at n = 3 + u have one sign); u_3/u_2 = 3/2 >= g(3) = 3/2 exactly; t_n <= 0 for every integer n in [4, +inf) (exact; Taylor shift: the coefficients of t_n at n = 4 + u have one sign); and s_n + t_n / g(n-1) - g(n) >= 0 for every integer n in [4, +inf) (exact; Taylor shift: the coefficients of s_n + t_n / g(n-1) - g(n) at n = 4 + u have one sign)","name":"degree_law","sign_decision":{"certificate":{"condition":"nonnegative","denominator":["-1","1"],"method":{"kind":"taylor_shift","shifted_denominator":["3","1"],"shifted_numerator":[]},"numerator":[],"range":{"first":"4","last":null}},"decision":"holds"},"statement":"deg P_n - deg P_(n-1) is 0 or 1 and P_n, P_(n-2) have positive leading coefficients (after the sign normalization) for every n >= 3: full growth (deg P_n = deg P_(n-1) + 1); l_n = ([x^1] A_n) l_(n-1) + ([x^2] B_n) l_(n-2) when deg P_(n-1) - deg P_(n-2) = 1 (then deg P_n - deg P_(n-1) = 1)","status":{"kind":"verified"}},{"evidence":"B_n = p_2 x^2 + p_1 x + p_0 with p_2 <= 0, p_0 <= 0 and p_1^2 <= 4 p_2 p_0 (so B_n <= 0 on the real line): p_2 = [x^2] B_n <= 0 for every integer n in [3, +inf) (exact; Taylor shift: the coefficients of p_2 = [x^2] B_n at n = 3 + u have one sign); p_0 = [x^0] B_n <= 0 for every integer n in [3, +inf) (exact; Taylor shift: the coefficients of p_0 = [x^0] B_n at n = 3 + u have one sign); p_1^2 - 4 p_2 p_0 <= 0 for every integer n in [3, +inf) (exact; Taylor shift: the coefficients of p_1^2 - 4 p_2 p_0 at n = 3 + u have one sign)","name":"lag_coefficient_nonpositive","statement":"B_n(x) <= 0 for every real x and every n >= 3","status":{"kind":"verified"}}],"lean_declarations":["RealRooted.MaWang.strictInterl_of_interlaces_evalCoeff_nonpos"],"lean_replay":"not_attempted","normal_form":"Q_n = A_n(x) Q_(n-1) + B_n(x) Q_(n-2) for n >= 3, with A_n(x) = (2) x, B_n(x) = (-1) + (-1) x^2; Q_n = x^(n - 1) P_n(1/x) for n >= 1 (the reversal at the nominal degree deg P_1 + n - 1, an upper bound for deg P_n), which satisfies the rule below","recurrence":{"first_index":1,"initial_polynomials":[["1"],["2"]],"recurrence":{"terms":[{"coeff":{"coeffs":[["2"]]},"deriv_order":0,"offset":1,"sign":"none"},{"coeff":{"coeffs":[["-1","0","-1"]]},"deriv_order":0,"offset":2,"sign":"none"}]},"schema":"polytool.recurrence.v1"},"reference":"L. L. Liu and Y. Wang, Adv. Appl. Math. 38 (2007) 542-560, Theorem 2.1 and Corollary 2.4 (A unified approach to polynomial sequences with only real zeros; the lag row as the interlacer, b_n = 0), weak interlacing of consecutive rows, with nonnegativity of the coefficients replaced, where a root region is certified, by an exact root-location induction","schema":"polytool.recurrence-real-rootedness-theorem.v1","status":"proved","theorem":"liu_wang_three_term"}}