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 A280619 #17 Dec 23 2022 10:00:34
%S A280619 1,2,3,4,5,7,8,9,11,13,17,19,23,25,29,31,37,41,43,47,49,53,59,61,67,
%T A280619 71,73,79,83,89,97,101,103,107,109,113,121,127,131,137,139,149,151,
%U A280619 157,163,167,169,173,179,181,191,193,197,199,211,223,227,229,233,239,241
%N A280619 Integers m such that sigma(m) - eulerphi(m) <= 4*sqrt(m).
%C A280619 Equals {1, 8} union A000430 (primes and square of primes).
%C A280619 Equals 8 union A166684.
%H A280619 Indranil Ghosh, <a href="/A280619/b280619.txt">Table of n, a(n) for n = 1..10000</a>
%H A280619 Mathematical Reflections, <a href="https://www.awesomemath.org/wp-pdf-files/math-reflections/mr-2013-03/mr_2_2013_solutions.pdf">Solution to Problem O261</a>, Issue 3, 2013, p. 24.
%t A280619 Select[Range[250],DivisorSigma[1,#]-EulerPhi[#]<=4Sqrt[#]&] (* _Harvey P. Dale_, Jul 10 2018 *)
%o A280619 (PARI) isok(n) = sigma(n) - eulerphi(n) <= 4*sqrt(n); \\ _Michel Marcus_, Jan 06 2017
%Y A280619 A000430 is the main entry for this sequence.
%Y A280619 Cf. A000010, A000203, A166684.
%K A280619 nonn,easy
%O A280619 1,2
%A A280619 _Michel Marcus_, Jan 06 2017