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 A324393 #17 Dec 04 2020 09:21:59 %S A324393 0,0,1,0,1,0,1,0,2,0,1,0,1,2,3,0,1,0,1,0,1,2,1,0,2,2,3,3,1,2,1,0,2,0, %T A324393 3,0,1,2,2,0,1,0,1,3,5,2,1,0,2,2,3,3,1,2,2,4,2,2,1,0,1,2,3,0,3,0,1,0, %U A324393 2,4,1,0,1,2,4,3,3,2,1,0,3,2,1,0,3,2,3,4,1,4,3,0,3,2,3,0,1,4,4,3,1,2,1,4,4 %N A324393 a(n) is the number of such divisors d of n that A000120(d) does not divide n, where A000120(d) gives the binary weight of d. %C A324393 Number of such positive integers k that divide n but A000120(k) [the Hamming weight of k] does not divide n. %H A324393 Antti Karttunen, <a href="/A324393/b324393.txt">Table of n, a(n) for n = 1..65537</a> %H A324393 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a> %F A324393 a(n) = Sum_{d|n} [A000120(d) does not divide n], where [ ] is the Iverson bracket. %F A324393 a(n) = A000005(n) - A324392(n). %F A324393 a(p) = 1 for all odd primes p. %t A324393 a[n_] := DivisorSum[n, 1 &, !Divisible[n, DigitCount[#, 2, 1]] &]; Array[a, 100] (* _Amiram Eldar_, Dec 04 2020 *) %o A324393 (PARI) A324393(n) = sumdiv(n, d, !!(n%hammingweight(d))); %Y A324393 Cf. A000005, A000120, A324392, A306263 (positions of zeros). %Y A324393 Cf. also A093653, A192895, A266342, A292257. %K A324393 nonn,base %O A324393 1,9 %A A324393 _Antti Karttunen_, Mar 05 2019