A359434 Numbers k >= 1 such that k * phi(k) / (k + phi(k)) is an integer, where phi(k) = A000010(k).

12, 24, 36, 48, 72, 96, 108, 126, 144, 176, 192, 216, 252, 288, 324, 352, 378, 384, 432, 504, 576, 648, 704, 756, 768, 864, 882, 972, 1008, 1134, 1152, 1296, 1408, 1512, 1536, 1728, 1764, 1936, 1944, 2016, 2268, 2304, 2592, 2646, 2752, 2816, 2916

Offset

1,1

Comments

For k >= 12, A003586 is a subsequence.

Links

Table of n, a(n) for n=1..47.

Example

k = 12 : 12 * phi(12) / (12 + phi(12)) = 12 * 4 / (12 + 4) = 3, thus 12 is a term.

Mathematica

Select[Range[3000], Divisible[#*(phi = EulerPhi[#]), # + phi] &] (* Amiram Eldar, Dec 31 2022 *)

Crossrefs

Cf. A000010, A003586, A033845.

Sequence in context: A364710 A367338 A069056 * A358693 A371413 A019550

Adjacent sequences: A359431 A359432 A359433 * A359435 A359436 A359437

Keyword

nonn

Author

Ctibor O. Zizka, Dec 31 2022

Status

approved