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A048747 Factor n, divide sum of divisors by number of divisors; append n to sequence if quotient is integral and not previously seen. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

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.

MATHEMATICA

(Select[{Mean[Divisors[#]], #}& /@ Select[Range[300], CompositeQ], IntegerQ[#[[1]]]&] // Sort // Split[#, #1[[1]] == #2[[1]]&]&)[[All, 1]][[All, 2]] // Sort (* Jean-Fran├žois Alcover, Oct 31 2017 *)

CROSSREFS

Gives first occurrence of terms in A023883.

Cf. A000005, A000203, A048748.

Sequence in context: A072204 A037177 A255217 * A175678 A173870 A101567

Adjacent sequences:  A048744 A048745 A048746 * A048748 A048749 A048750

KEYWORD

nonn

AUTHOR

Enoch Haga

STATUS

approved

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Last modified February 27 03:50 EST 2020. Contains 332299 sequences. (Running on oeis4.)