[Solution to the problem] 5371[: a lower bound for a sum of squares]

School Science and Mathematics An inequality involving a sum of squares 5371: Proposed by Jos´e Luis D´ıaz-Barrero, BarcelonaTech, Barcelona, Spain. Let a1, a2, . . . , anbe n≥4 positive real numbers. Prove that a1 an+a22 +a2 a1+a32 +. . . +an an−1+a12 ≥4 n (Vol. 115, No. 7, November 2015, pp. 1.)