A373527 Odd numbers k such that k and k+2 both have at least two divisors with the same value of the Euler totient function (A000010).

2107, 11275, 42651, 68733, 90153, 99123, 123633, 213003, 226825, 242305, 262143, 272853, 292873, 295405, 308007, 313443, 376675, 376803, 378693, 390115, 427425, 471293, 473263, 524797, 525481, 556983, 579535, 591325, 618469, 638163, 663325, 669123, 699853, 731815

Offset: 1

Author

Amiram Eldar, Jun 08 2024

Keywords

• nonn

Comments

Numbers k such that k and k+2 are both in A359563.

Links

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

Crossrefs

Subsequence of A359563.

A373528 is a subsequence.

Cf. A000010, A102190.

Programs

Mathematica

q[n_] := q[n] = UnsameQ @@ EulerPhi[Divisors[n]]; Select[Range[1, 10^6, 2], ! q[#] && ! q[# + 2] &]

PARI

is(k) = k>1 && k%2 && numdiv(k) > #Set(apply(x->eulerphi(x), divisors(k)));
lista(kmax) = {my(q1 = 0, q2); forstep(k = 3, kmax, 2, q2 = is(k); if(q1 && q2, print1(k-2, ", ")); q1 = q2);}