A330429 Numbers k such that phi(k) = phi(k+9), where phi (A000010) is Euler's totient function.

9, 15, 1005079920836, 13695542245376, 26160864154416, 27402841561095, 27599063056565, 110263115897935, 124632211478775, 127400054266476, 154090744843026, 205849483744896, 231019991767556, 339938754880725, 459718637643265, 632733228632505, 646552697065275, 683008674773416, 884965354448175

Offset

1,1

Comments

a(20) > 10^15.

Links

Table of n, a(n) for n=1..19.

Kevin Ford, Solutions of phi(n)=phi(n+k) and sigma(n)=sigma(n+k), arXiv:2002.12155 [math.NT], 2020.

S. W. Graham, J. J. Holt, and C. Pomerance, On the solutions to phi(n) = phi(n+k), Number Theory in Progress, K. Gyory, H. Iwaniec, and J. Urbanowicz, eds., vol. 2, de Gruyter, Berlin and New York, 1999, pp. 867-882.

Crossrefs

Cf. A000010, A007015.

Cf. A001274, A001494, A330251, A179186, A179187, A179188, A179189, A179202.

Cf. A276503, A276504, A217139.

Sequence in context: A078794 A373332 A093595 * A372213 A215418 A133816

Adjacent sequences: A330426 A330427 A330428 * A330430 A330431 A330432

Keyword

nonn

Author

Giovanni Resta, Mar 01 2020

Status

approved