A377951 Numbers k such that k | A057643(k) and (k+1) | A057643(k+1).

1, 799799, 1204280, 2460975, 3382379, 6116175, 7050120, 8070699, 13339424, 20966049, 28460600, 41265680, 41463135, 52404624, 66108399, 68919080, 72946224, 81102944, 84479680, 102971924, 106663304, 110791736, 112375899, 115225439, 118333215, 131115984, 132073424

Offset: 1

Author

Amiram Eldar, Nov 12 2024

Keywords

• nonn

Comments

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

Links

• Amiram Eldar, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A057643.

Subsequence of A377950.

Similar sequences: A355332, A377949, A377953.

Programs

Mathematica

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

PARI

is1(k) = !(lcm(apply(x->x+1, divisors(k))) % k);
lista(kmax) = {my(q1 = is1(1), q2); for(k = 2, kmax, q2 = is1(k); if(q1 && q2, print1(k-1, ", ")); q1 = q2);}