A071593 Number of 1's in binary representation of n equals tau(n), the number of divisors of n.

1, 3, 5, 15, 17, 25, 27, 39, 46, 49, 51, 57, 58, 63, 77, 85, 86, 106, 141, 142, 166, 175, 177, 178, 201, 202, 207, 209, 226, 243, 245, 255, 257, 267, 278, 289, 291, 298, 305, 323, 326, 329, 363, 393, 394, 417, 423, 519, 526, 529, 533, 537, 538, 553, 554, 562

Offset

1,2

Links

Gheorghe Coserea, Table of n, a(n) for n = 1..51000

Example

85=1010101 in base 2 and 85 has 4 divisors hence 85 is in the sequence.

Mathematica

Select[Range[600], DigitCount[#, 2, 1]==DivisorSigma[0, #]&] (* Harvey P. Dale, Aug 22 2018 *)

Prog

(PARI) for(n=1, 1000, if(sum(i=1, length(binary(n)), component(binary(n), i))==numdiv(n), print1(n, ", ")))
(PARI) Vec(select(x->numdiv(x) == hammingweight(x), vector(562, k, k))  \\ Gheorghe Coserea, Oct 26 2016

Crossrefs

Sequence in context: A103127 A103192 A097856 * A192794 A293001 A018358

Adjacent sequences: A071590 A071591 A071592 * A071594 A071595 A071596

Keyword

base,easy,nonn

Author

Benoit Cloitre, Jun 01 2002

Status

approved