***************************************************************************** * www.FindStat.org - The Combinatorial Statistic Finder * * * * Copyright (C) 2019 The FindStatCrew * * * * This information is distributed in the hope that it will be useful, * * but WITHOUT ANY WARRANTY; without even the implied warranty of * * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. * ***************************************************************************** ----------------------------------------------------------------------------- Statistic identifier: St000755 ----------------------------------------------------------------------------- Collection: Integer partitions ----------------------------------------------------------------------------- Description: The number of real roots of the characteristic polynomial of a linear recurrence associated with an integer partition. Consider the recurrence $$f(n)=\sum_{p\in\lambda} f(n-p).$$ This statistic returns the number of distinct real roots of the associated characteristic polynomial. For example, the partition $(2,1)$ corresponds to the recurrence $f(n)=f(n-1)+f(n-2)$ with associated characteristic polynomial $x^2-x-1$, which has two real roots. ----------------------------------------------------------------------------- References: [1] [[wikipedia:Recurrence_relation#Roots_of_the_characteristic_polynomial]] ----------------------------------------------------------------------------- Code: def statistic(m): """ Return the number of real roots of x^m_k = x^{m_k-m_1} + x^{m_k-m_2} + ... + 1 without multiplicities. """ if len(m) == 0: return None R. = PolynomialRing(ZZ) mk = max(m) eq = x^mk - sum(x^(mk-e) for e in m) return eq.number_of_real_roots() ----------------------------------------------------------------------------- Statistic values: [1] => 1 [2] => 2 [1,1] => 1 [3] => 1 [2,1] => 2 [1,1,1] => 1 [4] => 2 [3,1] => 1 [2,2] => 2 [2,1,1] => 2 [1,1,1,1] => 1 [5] => 1 [4,1] => 2 [3,2] => 1 [3,1,1] => 1 [2,2,1] => 2 [2,1,1,1] => 2 [1,1,1,1,1] => 1 [6] => 2 [5,1] => 1 [4,2] => 2 [4,1,1] => 2 [3,3] => 1 [3,2,1] => 1 [3,1,1,1] => 1 [2,2,2] => 2 [2,2,1,1] => 2 [2,1,1,1,1] => 2 [1,1,1,1,1,1] => 1 [7] => 1 [6,1] => 2 [5,2] => 1 [5,1,1] => 1 [4,3] => 2 [4,2,1] => 2 [4,1,1,1] => 2 [3,3,1] => 1 [3,2,2] => 3 [3,2,1,1] => 1 [3,1,1,1,1] => 1 [2,2,2,1] => 2 [2,2,1,1,1] => 2 [2,1,1,1,1,1] => 2 [1,1,1,1,1,1,1] => 1 [8] => 2 [7,1] => 1 [6,2] => 2 [6,1,1] => 2 [5,3] => 1 [5,2,1] => 1 [5,1,1,1] => 1 [4,4] => 2 [4,3,1] => 2 [4,2,2] => 2 [4,2,1,1] => 2 [4,1,1,1,1] => 2 [3,3,2] => 1 [3,3,1,1] => 1 [3,2,2,1] => 1 [3,2,1,1,1] => 1 [3,1,1,1,1,1] => 1 [2,2,2,2] => 2 [2,2,2,1,1] => 2 [2,2,1,1,1,1] => 2 [2,1,1,1,1,1,1] => 2 [1,1,1,1,1,1,1,1] => 1 [9] => 1 [8,1] => 2 [7,2] => 1 [7,1,1] => 1 [6,3] => 2 [6,2,1] => 2 [6,1,1,1] => 2 [5,4] => 1 [5,3,1] => 1 [5,2,2] => 3 [5,2,1,1] => 1 [5,1,1,1,1] => 1 [4,4,1] => 2 [4,3,2] => 2 [4,3,1,1] => 2 [4,2,2,1] => 2 [4,2,1,1,1] => 2 [4,1,1,1,1,1] => 2 [3,3,3] => 1 [3,3,2,1] => 1 [3,3,1,1,1] => 1 [3,2,2,2] => 3 [3,2,2,1,1] => 1 [3,2,1,1,1,1] => 1 [3,1,1,1,1,1,1] => 1 [2,2,2,2,1] => 2 [2,2,2,1,1,1] => 2 [2,2,1,1,1,1,1] => 2 [2,1,1,1,1,1,1,1] => 2 [1,1,1,1,1,1,1,1,1] => 1 [10] => 2 [9,1] => 1 [8,2] => 2 [8,1,1] => 2 [7,3] => 1 [7,2,1] => 1 [7,1,1,1] => 1 [6,4] => 2 [6,3,1] => 2 [6,2,2] => 2 [6,2,1,1] => 2 [6,1,1,1,1] => 2 [5,5] => 1 [5,4,1] => 1 [5,3,2] => 1 [5,3,1,1] => 1 [5,2,2,1] => 1 [5,2,1,1,1] => 1 [5,1,1,1,1,1] => 1 [4,4,2] => 2 [4,4,1,1] => 2 [4,3,3] => 2 [4,3,2,1] => 2 [4,3,1,1,1] => 2 [4,2,2,2] => 2 [4,2,2,1,1] => 2 [4,2,1,1,1,1] => 2 [4,1,1,1,1,1,1] => 2 [3,3,3,1] => 1 [3,3,2,2] => 1 [3,3,2,1,1] => 1 [3,3,1,1,1,1] => 1 [3,2,2,2,1] => 3 [3,2,2,1,1,1] => 1 [3,2,1,1,1,1,1] => 1 [3,1,1,1,1,1,1,1] => 1 [2,2,2,2,2] => 2 [2,2,2,2,1,1] => 2 [2,2,2,1,1,1,1] => 2 [2,2,1,1,1,1,1,1] => 2 [2,1,1,1,1,1,1,1,1] => 2 [1,1,1,1,1,1,1,1,1,1] => 1 [11] => 1 [10,1] => 2 [9,2] => 1 [9,1,1] => 1 [8,3] => 2 [8,2,1] => 2 [8,1,1,1] => 2 [7,4] => 1 [7,3,1] => 1 [7,2,2] => 3 [7,2,1,1] => 1 [7,1,1,1,1] => 1 [6,5] => 2 [6,4,1] => 2 [6,3,2] => 2 [6,3,1,1] => 2 [6,2,2,1] => 2 [6,2,1,1,1] => 2 [6,1,1,1,1,1] => 2 [5,5,1] => 1 [5,4,2] => 3 [5,4,1,1] => 1 [5,3,3] => 1 [5,3,2,1] => 1 [5,3,1,1,1] => 1 [5,2,2,2] => 3 [5,2,2,1,1] => 1 [5,2,1,1,1,1] => 1 [5,1,1,1,1,1,1] => 1 [4,4,3] => 2 [4,4,2,1] => 2 [4,4,1,1,1] => 2 [4,3,3,1] => 2 [4,3,2,2] => 2 [4,3,2,1,1] => 2 [4,3,1,1,1,1] => 2 [4,2,2,2,1] => 2 [4,2,2,1,1,1] => 2 [4,2,1,1,1,1,1] => 2 [4,1,1,1,1,1,1,1] => 2 [3,3,3,2] => 1 [3,3,3,1,1] => 1 [3,3,2,2,1] => 1 [3,3,2,1,1,1] => 1 [3,3,1,1,1,1,1] => 1 [3,2,2,2,2] => 3 [3,2,2,2,1,1] => 1 [3,2,2,1,1,1,1] => 1 [3,2,1,1,1,1,1,1] => 1 [3,1,1,1,1,1,1,1,1] => 1 [2,2,2,2,2,1] => 2 [2,2,2,2,1,1,1] => 2 [2,2,2,1,1,1,1,1] => 2 [2,2,1,1,1,1,1,1,1] => 2 [2,1,1,1,1,1,1,1,1,1] => 2 [1,1,1,1,1,1,1,1,1,1,1] => 1 [12] => 2 [11,1] => 1 [10,2] => 2 [10,1,1] => 2 [9,3] => 1 [9,2,1] => 1 [9,1,1,1] => 1 [8,4] => 2 [8,3,1] => 2 [8,2,2] => 2 [8,2,1,1] => 2 [8,1,1,1,1] => 2 [7,5] => 1 [7,4,1] => 1 [7,3,2] => 1 [7,3,1,1] => 1 [7,2,2,1] => 1 [7,2,1,1,1] => 1 [7,1,1,1,1,1] => 1 [6,6] => 2 [6,5,1] => 2 [6,4,2] => 2 [6,4,1,1] => 2 [6,3,3] => 2 [6,3,2,1] => 2 [6,3,1,1,1] => 2 [6,2,2,2] => 2 [6,2,2,1,1] => 2 [6,2,1,1,1,1] => 2 [6,1,1,1,1,1,1] => 2 [5,5,2] => 1 [5,5,1,1] => 1 [5,4,3] => 1 [5,4,2,1] => 1 [5,4,1,1,1] => 1 [5,3,3,1] => 1 [5,3,2,2] => 1 [5,3,2,1,1] => 1 [5,3,1,1,1,1] => 1 [5,2,2,2,1] => 2 [5,2,2,1,1,1] => 1 [5,2,1,1,1,1,1] => 1 [5,1,1,1,1,1,1,1] => 1 [4,4,4] => 2 [4,4,3,1] => 2 [4,4,2,2] => 2 [4,4,2,1,1] => 2 [4,4,1,1,1,1] => 2 [4,3,3,2] => 2 [4,3,3,1,1] => 2 [4,3,2,2,1] => 2 [4,3,2,1,1,1] => 2 [4,3,1,1,1,1,1] => 2 [4,2,2,2,2] => 2 [4,2,2,2,1,1] => 2 [4,2,2,1,1,1,1] => 2 [4,2,1,1,1,1,1,1] => 2 [4,1,1,1,1,1,1,1,1] => 2 [3,3,3,3] => 1 [3,3,3,2,1] => 1 [3,3,3,1,1,1] => 1 [3,3,2,2,2] => 2 [3,3,2,2,1,1] => 1 [3,3,2,1,1,1,1] => 1 [3,3,1,1,1,1,1,1] => 1 [3,2,2,2,2,1] => 3 [3,2,2,2,1,1,1] => 1 [3,2,2,1,1,1,1,1] => 1 [3,2,1,1,1,1,1,1,1] => 1 [3,1,1,1,1,1,1,1,1,1] => 1 [2,2,2,2,2,2] => 2 [2,2,2,2,2,1,1] => 2 [2,2,2,2,1,1,1,1] => 2 [2,2,2,1,1,1,1,1,1] => 2 [2,2,1,1,1,1,1,1,1,1] => 2 [2,1,1,1,1,1,1,1,1,1,1] => 2 [1,1,1,1,1,1,1,1,1,1,1,1] => 1 [5,4,3,1] => 1 [5,4,2,2] => 3 [5,4,2,1,1] => 1 [5,3,3,2] => 1 [5,3,3,1,1] => 1 [5,3,2,2,1] => 1 [4,4,3,2] => 2 [4,4,3,1,1] => 2 [4,4,2,2,1] => 2 [4,3,3,2,1] => 2 [5,4,3,2] => 1 [5,4,3,1,1] => 1 [5,4,2,2,1] => 3 [5,3,3,2,1] => 1 [4,4,3,2,1] => 2 [5,4,3,2,1] => 1 ----------------------------------------------------------------------------- Created: Apr 08, 2017 at 16:43 by Martin Rubey ----------------------------------------------------------------------------- Last Updated: Dec 30, 2017 at 22:57 by Martin Rubey