cp's OEIS Frontend

A342503 Numbers k such that k divides A340740(k).

%I A342503 #38 Feb 07 2023 20:46:03
%S A342503 1,2,3,4,6,19,48,111,4630,5428,13569,41628,87659,108990,555716,751863,
%T A342503 973813,5124585,8663699,19545678,24330343
%N A342503 Numbers k such that k divides A340740(k).
%e A342503 a(8) = 111 is a term because 111 divides A340740(111) = 444.
%p A342503 filter:= proc(n) local k; add(`if`(igcd(k,n)=1, (n-k) mod k, 0),k=1..n/2) mod n = 0 end proc:
%p A342503 select(filter, [$1..10^5]);
%o A342503 (Python)
%o A342503 from math import gcd
%o A342503 A342503_list = [k for k in range(1,10**4) if sum(k % i for i in range(1,k//2+1) if gcd(i,k) == 1) % k == 0] # _Chai Wah Wu_, Mar 18 2021
%Y A342503 Cf. A340740.
%K A342503 nonn,more
%O A342503 1,2
%A A342503 _J. M. Bergot_ and _Robert Israel_, Mar 16 2021
%E A342503 a(14)-a(17) from _Chai Wah Wu_, Mar 18 2021
%E A342503 a(18)-a(19) from _Martin Ehrenstein_, May 14 2021
%E A342503 a(20) from _Kevin P. Thompson_, Jan 19 2023
%E A342503 a(21) from _Kevin P. Thompson_, Feb 07 2023