isabelle/valid/induction_sum2kp1npqsqm1.thy (12 lines of code) (raw):

(* Authors: Wenda Li *) theory induction_sum2kp1npqsqm1 imports Complex_Main "HOL-Computational_Algebra.Computational_Algebra" "HOL-Number_Theory.Number_Theory" begin theorem induction_sum2kp1npqsqm1: fixes n :: nat shows "(\<Sum> k<n. 2 * k + 3) = (n + 1)^2 - 1" sorry end