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

1,2

Comments

Integers m such that A327153(m) = 1.

Links

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

Prog

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

Crossrefs

Cf. A000203, A064987, A327153, A337873.

Subsequence of A327165.

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

Cf. A338519 (similar for number of divisors).

Sequence in context: A009242 A032647 A327165 * A339472 A348034 A086792

Adjacent sequences: A338517 A338518 A338519 * A338521 A338522 A338523

Keyword

nonn

Author

Michel Marcus, Nov 01 2020

Status

approved