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 A046687 #18 Jan 15 2024 12:21:02 %S A046687 1,2,3,4,5,7,8,9,11,13,15,16,17,18,19,21,23,25,27,29,31,32,33,35,37, %T A046687 39,41,43,45,47,49,50,51,53,55,57,59,61,64,65,67,69,71,72,73,77,79,81, %U A046687 83,85,87,89,91,93,95,97,98,99,100,101,103,105,107,109,111,113,115,119 %N A046687 Numbers k such that k and sum of 4th powers of divisors of k are relatively prime. %C A046687 All even terms are either squares or doubled squares. - _Ivan Neretin_, Dec 30 2015 %C A046687 The asymptotic density of this sequence is 0 (Dressler, 1974). - _Amiram Eldar_, Jul 23 2020 %H A046687 Ivan Neretin, <a href="/A046687/b046687.txt">Table of n, a(n) for n = 1..10076</a> %H A046687 Robert E. Dressler, <a href="https://doi.org/10.4153/CMB-1974-019-5">On a theorem of Niven</a>, Canadian Mathematical Bulletin, Vol. 17, No. 1 (1974), pp. 109-110. %t A046687 Select[Range[120], GCD[#, DivisorSigma[4, #]] == 1 &] (* _Ivan Neretin_, Dec 30 2015 *) %t A046687 Select[Range[150],CoprimeQ[#,DivisorSigma[4,#]]&] (* _Harvey P. Dale_, Jan 15 2024 *) %o A046687 (PARI) isok(n) = gcd(n, sigma(n, 4)) == 1; \\ _Michel Marcus_, Dec 20 2013 %Y A046687 Cf. A001159, A046684, A046686. %K A046687 nonn %O A046687 1,2 %A A046687 _Labos Elemer_