CollapseProblem 1073Let A(x)A(x)A(x) count the number of composite u<xu<xu<x such that n!+1≡0(modu)n!+1\equiv 0\pmod{u}n!+1≡0(modu) for some nnn. Is it true that A(x)≤xo(1)A(x)\leq x^{o(1)}A(x)≤xo(1)?Source: erdosproblems.com/1073Number theoryWiki pageStatusOpenNo claim settles this problem.ReferencesHaSu02Hardy, G. E. and Subbarao, M. V., A modified problem of Pillai and some related questions. Amer. Math. Monthly (2002), 554-559.