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 A179872 #17 May 25 2025 09:23:34
%S A179872 3,4,6,7,8,9,12,13,14,15,16,18,19,20,21,24,25,26,27,28,30,31,32,33,35,
%T A179872 36,37,38,39,40,42,43,44,45,48,49,50,51,52,54,56,57,60,61,62,63,64,65,
%U A179872 66,67,68,69,70,72,73,74,75,76,77,78,79,80,81,84,86,87,88
%N A179872 Numbers h such that antiharmonic mean B(h) of the numbers k < h such that gcd(k, h) = 1 is not integer.
%C A179872 Numbers h such that B(h) = A053818(h) / A023896(h) = A175505(h) / A175506(h) is not integer.
%C A179872 Numbers h such that A175506(h) > 1.
%C A179872 Complement of A179871.
%C A179872 Union of A007645 and A179891.
%H A179872 Amiram Eldar, <a href="/A179872/b179872.txt">Table of n, a(n) for n = 1..10000</a>
%e A179872 a(6) = 9 because B(9) = A053818(9) / A023896(9) = 159/27 = 53/9 (not integer).
%o A179872 (PARI) isok(k) = {my(f = factor(k)); if(k == 1, 0, denominator(2*k/3 + (1/3) * prod(i = 1, #f~, 1 - f[i, 1])/eulerphi(f)) > 1);} \\ _Amiram Eldar_, May 25 2025
%Y A179872 Cf. A179871, A179873, A179874, A179875, A179876, A179877, A179878, A179879, A179880, A179882, A179883, A179884, A179885, A179886, A179887, A179890, A179891.
%K A179872 nonn
%O A179872 1,1
%A A179872 _Jaroslav Krizek_, Jul 30 2010, Jul 31 2010
%E A179872 More terms from _Amiram Eldar_, May 25 2025