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A048747
Factor composite 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
OFFSET
1,1
LINKS
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-François Alcover, Oct 31 2017 *)
CROSSREFS
Gives first occurrence of terms in A023883.
Sequence in context: A037177 A351975 A255217 * A175678 A173870 A101567
KEYWORD
nonn
AUTHOR
EXTENSIONS
Title clarified by Sean A. Irvine, Jul 03 2021
STATUS
approved