A048747 Factor composite n, divide sum of divisors by number of divisors; append n to sequence if quotient is integral and not previously seen.

6, 14, 20, 21, 22, 27, 33, 38, 39, 45, 46, 49, 57, 62, 65, 85, 86, 87, 91, 93, 94, 99, 111, 116, 118, 123, 125, 129, 133, 134, 141, 142, 150, 158, 164, 166, 169, 183, 185, 188, 201, 206, 207, 213, 214, 215, 217, 219, 236, 237, 249, 254, 259, 261, 262, 267, 278

Offset: 1

Author

Enoch Haga

Keywords

• nonn

Examples

			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.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Gives first occurrence of terms in A023883.

Cf. A000005, A000203, A048748.

Programs

Mathematica

(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 *)

Extensions

Title clarified by Sean A. Irvine, Jul 03 2021