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A268373 Numbers other than prime powers divisible by the sum of the cubes of their prime divisors. 2

%I #17 Sep 08 2019 10:05:29

%S 378,480,756,960,1134,1440,1512,1920,2268,2400,2548,2646,2880,3024,

%T 3402,3840,4320,4536,4800,5096,5292,5760,6048,6804,7200,7680,7938,

%U 8640,9072,9600,10192,10206,10584,11520,12000,12096,12960,13608,14400,15360,15876,17280,17836,18144,18522,18711

%N Numbers other than prime powers divisible by the sum of the cubes of their prime divisors.

%C Koninck & Luca prove that this set is infinite. - _Charles R Greathouse IV_, Feb 03 2016

%H Amiram Eldar, <a href="/A268373/b268373.txt">Table of n, a(n) for n = 1..10000</a>

%H Jean-Marie de Koninck, Florian Luca, <a href="https://doi.org/10.1016/j.jnt.2007.01.010">Integers divisible by sums of powers of their prime factors</a>, Journal of Number Theory, Volume 128, Issue 3 (March 2008), pp. 557-563.

%e The prime factors of 480 are 2, 3 and 5. The sum of their cubes is 2^3+3^3+5^3=160, and 480 is divisible by 160.

%t Select[Range[10^4], Length[(p = FactorInteger[#][[;;,1]])] > 1 && Divisible[#, Total[p^3]] &] (* _Amiram Eldar_, Sep 05 2019 *)

%o (PARI) isok(n) = my(f = factor(n)[,1]) ; (#f>2) && ((n % sum(k=1, #f, f[k]^3)) == 0);

%Y Cf. A066031, A190882.

%K nonn

%O 1,1

%A _Michel Marcus_, Feb 03 2016

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Last modified April 25 03:15 EDT 2024. Contains 371964 sequences. (Running on oeis4.)