A338520 Integers that can be expressed as a product d*sigma(d), where sigma is the sum of divisors function, in a single way.

1, 6, 12, 28, 30, 56, 72, 117, 120, 132, 180, 182, 306, 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

Offset: 1

Author

Michel Marcus, Nov 01 2020

Keywords

• nonn

Comments

Integers m such that A327153(m) = 1.

Links

• David A. Corneth, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A064987, A327153, A337873.

Subsequence of A327165.

Subsequences: A000396 (perfect numbers), A036690 (p*(p+1)).

Cf. A338519 (similar for number of divisors).

Programs

PARI

f(n) = sumdiv(n, d, d*sigma(d)==n); \\ A327153
isok(n) = f(n)==1;