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A341274 Composite numbers k that are divisible by (k mod sopfr(k))+floor(k/sopfr(k)), where sopfr = A001414. 1

%I #11 Feb 09 2021 11:48:07

%S 4,6,12,16,20,21,24,27,30,36,40,45,48,52,56,60,66,70,72,75,80,84,88,

%T 90,96,105,108,112,117,126,140,150,152,160,180,182,192,195,198,200,

%U 220,224,225,231,240,252,255,256,270,286,288,290,301,306,308,320,330,344,345,352,360,378,384,396,429

%N Composite numbers k that are divisible by (k mod sopfr(k))+floor(k/sopfr(k)), where sopfr = A001414.

%H Robert Israel, <a href="/A341274/b341274.txt">Table of n, a(n) for n = 1..10000</a>

%e a(5) = 20 is a term because sopfr(20) = 2*2+5 = 9, and 20 is divisible by (20 mod 9)+floor(20/9) = 4.

%p spf:= proc(n) local t; add(t[1]*t[2],t=ifactors(n)[2]) end proc:

%p filter:= proc(n) local s, m;

%p if isprime(n) then return false fi;

%p s:= spf(n);

%p m:= n mod s;

%p n mod (m + (n-m)/s) = 0

%p end proc:

%p select(filter, [$4..500]);

%Y Contains A190275.

%Y Cf. A001414.

%K nonn

%O 1,1

%A _J. M. Bergot_ and _Robert Israel_, Feb 08 2021

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Last modified July 27 16:15 EDT 2024. Contains 374650 sequences. (Running on oeis4.)