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 A229305 #18 Dec 11 2015 22:05:57
%S A229305 10,20,26,30,40,43,50,52,55,57,58,60,70,78,80,86,90,100,104,110,114,
%T A229305 116,120,129,130,136,140,150,155,156,160,165,170,171,172,174,180,182,
%U A229305 190,200,208,210,215,220,222,228,230,232,234,240,250,253,258,260,270
%N A229305 Numbers n such that A031971(42*n) <> n (mod 42*n).
%C A229305 Complement of A229301.
%C A229305 The asymptotic density is in [0.2091, 0.2317].
%C A229305 If n is in A then k*n is in A for all natural number k.
%C A229305 The numbers k = 1, 2, 6, 42, 1806, 47058, 2214502422, 8490421583559688410706771261086 = A230311 are the only values of k such that the set {n: A031971(k*n) == n (mod k*n)} is nonempty. Its smallest element is n = 1, 1, 1, 1, 1, 5, 5, 39607528021345872635 = A231409. [Comment corrected and expanded by _Jonathan Sondow_, Dec 10 2013]
%H A229305 Jose María Grau, A. M. Oller-Marcen, and J. Sondow, <a href="http://arxiv.org/abs/1309.7941">On the congruence 1^n + 2^n +... + n^n = d (mod n), where d divides n</a>
%t A229305 g[n_] := Mod[Sum[PowerMod[i, n, n], {i, n}], n]; Select[Range[100], !g[42*#] == # &]
%Y A229305 Cf. A014117 (numbers n such that A031971(n)==1 (mod n)).
%Y A229305 Cf. A229300 (numbers n such that A031971(1806*n)== n (mod n*1806)).
%Y A229305 Cf. A229301 (numbers n such that A031971(42*n) == n (mod 42*n)).
%Y A229305 Cf. A229302 (numbers n such that A031971(6*n) == n (mod 6*n)).
%Y A229305 Cf. A229303 (numbers n such that A031971(2*n) == n (mod 2*n)).
%Y A229305 Cf. A229304 (numbers n such that A031971(1806*n) <> n (mod n*1806)).
%Y A229305 Cf. A229305 (numbers n such that A031971(42*n) <> n (mod 42*n)).
%Y A229305 Cf. A229306 (numbers n such that A031971(6*n) <> n (mod 6*n)).
%Y A229305 Cf. A229307 (numbers n such that A031971(2*n) <> n (mod 2*n)).
%Y A229305 Cf. A229308 (primitive numbers in A229304).
%Y A229305 Cf. A229309 (primitive numbers in A229305).
%Y A229305 Cf. A229310 (primitive numbers in A229306).
%Y A229305 Cf. A229311 (primitive numbers in A229307).
%K A229305 nonn
%O A229305 1,1
%A A229305 _José María Grau Ribas_, Sep 23 2013