A377950 Numbers k that divide A057643(k) = lcm{d+1 : d|k}.

1, 2, 6, 12, 42, 60, 84, 120, 140, 156, 168, 210, 220, 240, 280, 312, 360, 420, 440, 462, 468, 504, 600, 630, 660, 720, 770, 780, 840, 924, 936, 1008, 1064, 1092, 1170, 1200, 1260, 1320, 1404, 1428, 1540, 1560, 1680, 1683, 1800, 1806, 1848, 1860, 1980, 2016, 2160

Offset: 1

Author

Amiram Eldar, Nov 12 2024

Keywords

• nonn
• easy

Comments

After the first term a(1) = 1, the next odd term is a(44) = 1683, the next term that is coprime to 6 is a(159) = 10465, and the next term that is coprime to 30 is a(1359) = 151487.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A057643.

A377951 is a subsequence.

Similar sequences: A056954, A355331, A377952.

Programs

Mathematica

Select[Range[2500], Divisible[LCM @@ (Divisors[#] + 1), #] &]

PARI

is(k) = !(lcm(apply(x->x+1, divisors(k))) % k);