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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).
2
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
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.
Sequence in context: A159812 A233729 A272770 * A284962 A146895 A300008
KEYWORD
nonn
AUTHOR
Amiram Eldar, Jun 08 2024
STATUS
approved