cp's OEIS Frontend

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.

A093687 Numbers k such that the total number of 1's in the binary expansion of all the divisors of k sets a new record.

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%I A093687 #16 Feb 15 2023 13:45:26
%S A093687 1,2,3,6,12,18,24,30,60,90,120,180,252,360,420,504,540,630,756,840,
%T A093687 1080,1260,1980,2520,3780,5040,6300,7560,12600,13860,15120,21420,
%U A093687 25200,27720,32760,41580,42840,49140,55440,65520,81900,83160,98280,128520,138600
%N A093687 Numbers k such that the total number of 1's in the binary expansion of all the divisors of k sets a new record.
%H A093687 Amiram Eldar, <a href="/A093687/b093687.txt">Table of n, a(n) for n = 1..120</a>
%t A093687 a[n_] := Plus @@ DigitCount[Divisors[n], 2, 1]; am = -1; c = 0; seq={}; Do[a1 = a[n]; If[a1 > am, am = a1; c++; AppendTo[seq, n]], {n, 1, 10^4}]; seq (* _Amiram Eldar_, Dec 17 2019 *)
%o A093687 (Python) # uses imports and definitions in A093653
%o A093687 from itertools import count, islice
%o A093687 def f(n): return A093653(n)
%o A093687 def agen(r=0): yield from ((m, r:=fm)[0] for m in count(1) if (fm:=f(m))>r)
%o A093687 print(list(islice(agen(), 45))) # _Michael S. Branicky_, Feb 15 2023
%Y A093687 Cf. A093653.
%K A093687 nonn,base
%O A093687 1,2
%A A093687 _Jason Earls_, May 16 2004