This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A071593 #19 Aug 20 2024 03:42:24 %S A071593 1,3,5,15,17,25,27,39,46,49,51,57,58,63,77,85,86,106,141,142,166,175, %T A071593 177,178,201,202,207,209,226,243,245,255,257,267,278,289,291,298,305, %U A071593 323,326,329,363,393,394,417,423,519,526,529,533,537,538,553,554,562 %N A071593 Number of 1's in binary representation of n equals tau(n), the number of divisors of n. %H A071593 Gheorghe Coserea, <a href="/A071593/b071593.txt">Table of n, a(n) for n = 1..51000</a> %e A071593 85=1010101 in base 2 and 85 has 4 divisors hence 85 is in the sequence. %t A071593 Select[Range[600],DigitCount[#,2,1]==DivisorSigma[0,#]&] (* _Harvey P. Dale_, Aug 22 2018 *) %o A071593 (PARI) for(n=1,1000,if(sum(i=1,length(binary(n)), component(binary(n),i))==numdiv(n),print1(n,","))) %o A071593 (PARI) Vec(select(x->numdiv(x) == hammingweight(x), vector(562, k, k))) \\ _Gheorghe Coserea_, Oct 26 2016 %K A071593 base,easy,nonn %O A071593 1,2 %A A071593 _Benoit Cloitre_, Jun 01 2002