A377950 - OEIS

%I #7 Nov 13 2024 17:22:41

%S 1,2,6,12,42,60,84,120,140,156,168,210,220,240,280,312,360,420,440,

%T 462,468,504,600,630,660,720,770,780,840,924,936,1008,1064,1092,1170,

%U 1200,1260,1320,1404,1428,1540,1560,1680,1683,1800,1806,1848,1860,1980,2016,2160

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

%C 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.

%H Amiram Eldar, <a href="/A377950/b377950.txt">Table of n, a(n) for n = 1..10000</a>

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

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

%Y Cf. A057643.

%Y A377951 is a subsequence.

%Y Similar sequences: A056954, A355331, A377952.

%K nonn,easy

%O 1,2

%A _Amiram Eldar_, Nov 12 2024