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A327165
Numbers n that have a divisor d such that sigma(d)*d is equal to n.
9
1, 6, 12, 28, 30, 56, 72, 117, 120, 132, 180, 182, 306, 336, 360, 380, 496, 552, 672, 702, 775, 792, 840, 870, 992, 1080, 1092, 1406, 1440, 1568, 1584, 1680, 1722, 1836, 1892, 2016, 2160, 2184, 2256, 2280, 2793, 2862, 3276, 3312, 3510, 3540, 3600, 3672, 3696, 3782, 3960, 4032, 4556, 4560, 4650, 5096, 5112, 5220
OFFSET
1,2
COMMENTS
Numbers n for which A327153(n) > 0.
Sequence A064987 sorted into ascending order, with duplicates removed.
All even terms of A000396 occur here.
LINKS
PROG
(PARI) isA327165(n) = { fordiv(n, d, if(n==d*sigma(d), return(1))); (0); };
(PARI) A327165list(up_to) = { my(res = List()); for(i = 1, sqrtint(up_to), c = i*sigma(i); if(c <= up_to, listput(res, c))); listsort(res, 1); Vec(res); }; \\ From David A. Corneth, Sep 18 2019
CROSSREFS
Cf. A000203, A000396, A064987, A327153, A327599 (subsequence of odd terms).
Sequence in context: A249670 A009242 A032647 * A338520 A339472 A348034
KEYWORD
nonn
AUTHOR
Antti Karttunen, Sep 18 2019
STATUS
approved