Summation of Euler function values over numbers of the form p-1 / D. V. Goryashin. // Vestnik Moskovskogo Universiteta. Seriya 1. Matematika. Mekhanika. 2009. ? 1. P. 64-66 [Moscow Univ. Math. Bulletin. Vol. 64, N 1, 2009. P. 41-43].

An asymptotic formula is proved for the sum of values of the Euler function on numbers of the form p-1 not exceeding x. The order of the remainder of the asymptotics corresponds to the modern bound for zeros of the zeta function.