A071601 Numbers k such that k and phi(k) have the same number of 1's in their binary representation.

1, 2, 4, 8, 9, 16, 18, 32, 33, 36, 49, 64, 65, 66, 69, 72, 77, 98, 99, 121, 128, 130, 132, 138, 141, 144, 145, 154, 169, 177, 196, 198, 209, 225, 242, 256, 260, 261, 264, 265, 276, 282, 288, 290, 297, 305, 308, 325, 338, 354, 361, 392, 396, 418, 441, 450, 484

Offset

1,2

Links

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

Example

676 = 1010100100 in base 2, phi(676) = 312 = 100111000 in base 2, hence 676 is in the sequence.

Mathematica

Select[Range[500], DigitCount[#, 2, 1]==DigitCount[EulerPhi[#], 2, 1]&] (* Harvey P. Dale, Jun 17 2021 *)

Prog

(PARI) for(n=1, 1000, if(sum(i=1, length(binary(n)), component(binary(n), i))==sum(i=1, length(binary(eulerphi(n))), component(binary(eulerphi(n)), i)), print1(n, ", ")))

Crossrefs

Cf. A000010, A000120, A295660.

Sequence in context: A320137 A324525 A175338 * A114400 A341742 A330710

Adjacent sequences: A071598 A071599 A071600 * A071602 A071603 A071604

Keyword

base,easy,nonn

Author

Benoit Cloitre, Jun 01 2002

Status

approved