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D preserves real-rootedness by Rolle's theorem and p + c p' is real-rooted for every real c by Rolle's theorem applied to e^(x/c) p; Polya--Schur 1914); when the coefficients of phi have one sign, coefficients of one sign stay of one sign; applied to phi(n, .) for each n","lean_route":null,"lean_declarations":["RealRooted.splits_add_C_mul_derivative_all","RealRooted.splits_C_mul_add_derivative","Polynomial.Splits.derivative"],"certificate_hash":"999fd87d376708486f42dcf329182cff45d8e941cda2a3297308109fa0548f8b","verification_polytool":"replayed","verification_lean":"not_attempted","claims":[{"claim":"real_rooted","from_index":0,"region":{"upper":{"closed":true,"value":"0"}}}],"premises":[{"position":0,"node_id":"n-4e0b19699f4cf0db","role":"sequence","name":"Triangular array T read by rows: T(n,0) = T(n,n) = 1 for all n >= 0, T(n,k) = T(n-1,k-1) + T(n-1,k) for odd n and 1< = k <= n-1, T(n,k) = T(n-1,k-1) + T(n-1,k) + T(n-2,k-1) for even n and 1 <= k <= n-1.","uses":{"claim":"real_rooted","from_index":0,"region":{"upper":{"closed":true,"value":"0"}}},"uses_text":"Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, 0]"}]}],"used_by":[],"used_by_total":0,"links":[],"oeis":[],"bfiles":[],"oeis_texts":[{"oeis_id":"","target":"node","first_row":0,"oeis_offset":0,"reversed":false,"trim_zeros":"none","regular_triangle":false,"rows_shown":10,"polytool_commit":"c48629374597092cc41ef4d6273f37991516f984","triangle_example":"Triangle begins:\n  0:  0;\n  1:  1;\n  2:  3,   2;\n  3:  4,   8,   3;\n  4:  6,  22,  18,    4;\n  5:  7,  34,  51,   28,    5;\n  6:  9,  60, 135,  120,   45,    6;\n  7: 10,  78, 225,  300,  195,   60,   7;\n  8: 12, 116, 432,  780,  720,  348,  84,   8;\n  9: 13, 140, 606, 1356, 1695, 1212, 490, 104, 9;\n","recurrence_sentence":"The row polynomials satisfy P(n,x) = -(1+6*x+11*x^2+6*x^3+x^4)*P(n-4,x) + (2+6*x+2*x^2)*P(n-2,x) for n >= 4, with P(0,x) = 0, P(1,x) = 1, P(2,x) = 3 + 2*x, P(3,x) = 4 + 8*x + 3*x^2.","mathematica":"P[0, x_] := 0;\nP[1, x_] := 1;\nP[2, x_] := 3 + 2*x;\nP[3, x_] := 4 + 8*x + 3*x^2;\nP[n_, x_] := P[n, x] = Expand[-(1 + 6*x + 11*x^2 + 6*x^3 + x^4)*P[n - 4, x] + (2 + 6*x + 2*x^2)*P[n - 2, x]];\nTable[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten","pari":"P(N) = {my(v = vector(N + 1)); v[1] = 0; v[2] = 1; v[3] = 3 + 2*x; v[4] = 4 + 8*x + 3*x^2; for(n = 4, N, my(i = n + 1); v[i] = -(1 + 6*x + 11*x^2 + 6*x^3 + x^4)*v[i - 4] + (2 + 6*x + 2*x^2)*v[i - 2]); v};\nrow(n, p) = {my(c = Vecrev(p)); c};\nT(N) = {my(v = P(N)); concat(vector(#v, i, row(i - 1, v[i])))};\nT(9)","reading":{"first_row":0,"offset":0,"reversed":false,"trim_zeros":"none","regular_triangle":false}}],"derivation":{"root":"n-4e0b19699f4cf0db","steps":["D"],"edges":["e-218f1af72daab700"],"text":"A026374 \u2192 D"},"headline":"A026374 \u2192 D","chain":null}