A377953 Numbers k such that k | A084190(k) and (k+1) | A084190(k+1).

310155, 2566025, 2853135, 5746455, 6515145, 7329608, 8459360, 11291091, 15446079, 16181535, 26782224, 26942475, 32364464, 34318844, 36951200, 38579442, 38596239, 38763900, 40564524, 41273154, 47308976, 47648600, 49309715, 50163735, 51177224, 52573520, 58524465, 63668079

Offset: 1

Author

Amiram Eldar, Nov 12 2024

Keywords

• nonn

Comments

Numbers k such that k and k+1 are both terms in A377952.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..1500

Crossrefs

Cf. A084190.

Subsequence of A377952.

Similar sequences: A355332, A377949, A377951.

Programs

Mathematica

q[n_] := q[n] = n == 1 || Divisible[LCM @@ (Rest @ Divisors[n] - 1), n] ; Select[Range[3*10^6], q[#] && q[# + 1] &]

PARI

is1(k) = !(lcm(apply(x -> if(x > 1, x-1, x), 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);}