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

1,1

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

Mathematica

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

Prog

(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); }

Crossrefs

Subsequence of A359563.

A373528 is a subsequence.

Cf. A000010, A102190.

Sequence in context: A159812 A233729 A272770 * A284962 A146895 A300008

Adjacent sequences: A373524 A373525 A373526 * A373528 A373529 A373530

Keyword

nonn

Author

Amiram Eldar, Jun 08 2024

Status

approved