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 A317480 #7 Aug 19 2018 18:14:35
%S A317480 1,614341,618233,1854699,11746427,26584019,35239281,79752057,85393399,
%T A317480 118082503,345592247,354247509,505096361,802597537,1036776741,
%U A317480 1062742527,1515289083,2149579159,2243567557,3695178641,5077547629,5250772527,6566252693,6730702671
%N A317480 Numbers m such that Sum_{k=1..m} 1/gcd(k,m) is an integer.
%C A317480 Also numbers n such that n | A057660(n).
%C A317480 a(1)-a(21) are taken from De Koninck's book.
%D A317480 Jean-Marie De Koninck, Those Fascinating Numbers, Amer. Math. Soc., 2009, page 265.
%t A317480 fun[p_, e_]:=(p^(2e+1)+1)/(p+1); aQ[n_] := Divisible[Times @@ (fun @@@ FactorInteger[n]), n]; Select[Range[10000000], aQ]
%o A317480 (PARI) xi(n) = {f = factor(n); for (i=1, #f~, p = f[i, 1]; e = f[i, 2]; f[i, 1] = (p^(2*e+1)+1)/(p+1); f[i, 2] = 1; ); factorback(f); } for(n=1, 1e7, if(xi(n) % n == 0, print(n)))
%Y A317480 Cf. A057660.
%K A317480 nonn
%O A317480 1,2
%A A317480 _Amiram Eldar_, Jul 29 2018