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A343357 7-rough abundant numbers. 1

%I #23 Apr 15 2021 04:52:00

%S 20169691981106018776756331,21373852696395930345517903,

%T 21975933054040886129898689,23476198863254546445077041,

%U 23782174126975753483041047,23836908704943476736166573,24137500239684251978741183,24272002214551310731350839,24955720586792192723783257,24986334842265665051802619

%N 7-rough abundant numbers.

%C Each term has at least A001276(4) = 15 distinct prime factors and A108227(4) = 18 prime factors counted with multiplicity. - _Jianing Song_, Apr 13 2021

%C The smallest term with exactly 15 distinct prime factors is a(830) = 465709156638373299218537971 = 7^3 * 11^2 * 13^2 * 17^2 * 19 * 23 * ... * 61. - _Jianing Song_, Apr 14 2021

%H David A. Corneth, <a href="/A343357/b343357.txt">Table of n, a(n) for n = 1..2187</a>

%e k = 20169691981106018776756331 is in the sequence as its smallest prime factor is at least 7 and it is abundant as sigma(k) > 2*k.

%o (PARI) is(n) = gcd(n, 30) == 1 && sigma(n) > 2*n

%Y Cf. A005101, A007775, A047802, A115414.

%K nonn

%O 1,1

%A _David A. Corneth_, Apr 12 2021

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Last modified April 25 13:12 EDT 2024. Contains 371969 sequences. (Running on oeis4.)