A327165 Numbers n that have a divisor d such that sigma(d)*d is equal to n.

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

Antti Karttunen, Table of n, a(n) for n = 1..10001

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

Adjacent sequences: A327162 A327163 A327164 * A327166 A327167 A327168

Keyword

nonn

Author

Antti Karttunen, Sep 18 2019

Status

approved