A377951 - OEIS

%I #12 Nov 16 2024 04:28:25

%S 1,799799,1204280,2460975,3382379,6116175,7050120,8070699,13339424,

%T 20966049,28460600,41265680,41463135,52404624,66108399,68919080,

%U 72946224,81102944,84479680,102971924,106663304,110791736,112375899,115225439,118333215,131115984,132073424

%N Numbers k such that k | A057643(k) and (k+1) | A057643(k+1).

%C Numbers k such that k and k+1 are both terms in A377950.

%H Amiram Eldar, <a href="/A377951/b377951.txt">Table of n, a(n) for n = 1..1000</a>

%t q[n_] := q[n] = Divisible[LCM @@ (Divisors[n] + 1), n]; Select[Range[4*10^6], q[#] && q[# + 1] &]

%o (PARI) is1(k) = !(lcm(apply(x->x+1, divisors(k))) % k);

%o lista(kmax) = {my(q1 = is1(1), q2); for(k = 2, kmax, q2 = is1(k); if(q1 && q2, print1(k-1, ", ")); q1 = q2);}

%Y Cf. A057643.

%Y Subsequence of A377950.

%Y Similar sequences: A355332, A377949, A377953.

%K nonn

%O 1,2

%A _Amiram Eldar_, Nov 12 2024