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 A007624 Numbers m such that the product of proper divisors of m = m^k, k>1. (Formerly M4824) 4
 12, 18, 20, 24, 28, 30, 32, 40, 42, 44, 45, 48, 50, 52, 54, 56, 60, 63, 66, 68, 70, 72, 75, 76, 78, 80, 84, 88, 90, 92, 96, 98, 99, 102, 104, 105, 108, 110, 112, 114, 116, 117, 120, 124, 126, 128, 130, 132, 135, 136, 138, 140, 147, 148, 150, 152, 153, 154 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, p. 23. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 FORMULA d(n) > 4 and even. a(n) = n + O(n/log n). - Charles R Greathouse IV, Oct 23 2015 MATHEMATICA ppdQ[n_]:=Module[{c=Log[n, Times@@Most[Divisors[n]]]}, c>1&&IntegerQ[c]]; Select[Range[2, 160], ppdQ] (* Harvey P. Dale, Mar 06 2012 *) Select[Range[154], EvenQ[(d = DivisorSigma[0, #])] && d > 4 &] (* Amiram Eldar, Nov 20 2019 *) CROSSREFS Cf. A000005, A007956. Sequence in context: A319229 A334160 A271345 * A036456 A102467 A126706 Adjacent sequences:  A007621 A007622 A007623 * A007625 A007626 A007627 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified June 1 09:49 EDT 2020. Contains 334760 sequences. (Running on oeis4.)