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Factor composite n, divide sum of divisors by number of divisors; append n to sequence if quotient is integral and not previously seen.
4

%I #21 Jul 04 2021 16:04:53

%S 6,14,20,21,22,27,33,38,39,45,46,49,57,62,65,85,86,87,91,93,94,99,111,

%T 116,118,123,125,129,133,134,141,142,150,158,164,166,169,183,185,188,

%U 201,206,207,213,214,215,217,219,236,237,249,254,259,261,262,267,278

%N Factor composite n, divide sum of divisors by number of divisors; append n to sequence if quotient is integral and not previously seen.

%H Amiram Eldar, <a href="/A048747/b048747.txt">Table of n, a(n) for n = 1..10000</a>

%e a(3)=20; for n=20 the sum of divisors is 42; number of divisors is 6; 42/6=7. The quotient 7 is the mean divisor and this is the first time that 7 has occurred.

%t (Select[{Mean[Divisors[#]], #}& /@ Select[Range[300], CompositeQ], IntegerQ[#[[1]]]&] // Sort // Split[#, #1[[1]] == #2[[1]]&]&)[[All, 1]][[All, 2]] // Sort (* _Jean-François Alcover_, Oct 31 2017 *)

%Y Gives first occurrence of terms in A023883.

%Y Cf. A000005, A000203, A048748.

%K nonn

%O 1,1

%A _Enoch Haga_

%E Title clarified by _Sean A. Irvine_, Jul 03 2021