W. Sierpiński asked in 1959 (see [4], pp. 200-201, cf. [2]) whether there exist infinitely many positive integers not of the form n - φ(n), where φ is the Euler function. We answer this question in the affirmative by proving Theorem. None of the numbers (k = 1, 2,...) is of the form n - φ(n).
@article{bwmeta1.element.bwnjournal-article-cmv68i1p55bwm, author = {J. Browkin and A. Schinzel}, title = {On integers not of the form n - $\phi$ (n)}, journal = {Colloquium Mathematicae}, volume = {68}, year = {1995}, pages = {55-58}, zbl = {0820.11003}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-cmv68i1p55bwm} }
Browkin, J.; Schinzel, A. On integers not of the form n - φ (n). Colloquium Mathematicae, Tome 68 (1995) pp. 55-58. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-cmv68i1p55bwm/
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