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A286876 Numbers n such that the set of prime divisors of n is equal to the set of prime divisors of sum of proper divisors of n while n is not in A027598. 1
24, 40, 216, 234, 360, 588, 2016, 3724, 4320, 4680, 6048, 6552, 9720, 11466, 22932, 54432, 58752, 97920, 99200, 108927, 137214, 167580, 185562, 217854, 297600, 309582, 435708, 448335, 524160, 544635, 637000, 804384, 871416, 931840, 1284192, 1384110, 1489752 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

108927 is the smallest odd term of this sequence.

LINKS

Table of n, a(n) for n=1..37.

EXAMPLE

24 is in the sequence because 24 = 2^3*3 and sum of proper divisors of 24 is 1 + 2 + 3 + 4 + 6 + 8 + 12 = 36 = 2^2*3^2 while sigma(24) = 60 is divisible by 5.

MATHEMATICA

Select[Range[1500000], And[UnsameQ @@ {#1, #2}, SameQ @@ {#1, #3}] & @@ Map[FactorInteger[#][[All, 1]] &, {#1, #2, #2 - #1} & @@ {#, DivisorSigma[1, #]}] &] (* Michael De Vlieger, Aug 02 2017 *)

PROG

(PARI) rad(n) = factorback(factorint(n)[, 1]);

isok(n) = rad(sigma(n)-n)==rad(n) && rad(sigma(n))!=rad(n);

CROSSREFS

Cf. A000203, A001065, A007947, A027598.

Sequence in context: A316271 A141717 A185742 * A181702 A304890 A264155

Adjacent sequences:  A286873 A286874 A286875 * A286877 A286878 A286879

KEYWORD

nonn

AUTHOR

Altug Alkan, Aug 02 2017

STATUS

approved

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Last modified June 19 04:44 EDT 2019. Contains 324217 sequences. (Running on oeis4.)