Almost all hyperharmonic numbers are not integers
On quotients of values of Euler's function on the Catalan numbers
In a recent work, Luca and Stănică examined quotients of the form View the MathML source, where φ is Euler's totient function and C0,C1,C2… is the sequence of the Catalan numbers. They observed that the number 4 (and analogously View the MathML source) appears noticeably often as a value of these quotients. We give an explanation of this phenomenon, based on Dickson's conjecture. It turns out not only that the value 4 is (in a certain sense) special in relation to the quotients View the MathML source, but also that the value 4k has similar “special” properties with respect to the quotients View the MathML source, and in particular we show that Dickson's conjecture implies that, for each k , the number 4k appears infinitely often as a value of the quotients View the MathML source.