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 A058075 #25 Aug 08 2020 08:23:38
%S A058075 1,2,3,4,7,8,9,15,16,18,24,25,31,35,36,48,63,64,72,80,81,97,99,100,
%T A058075 120,121,127,128,143,144,162,200,224,225,241,255,256,288,289,323,337,
%U A058075 399,400,483,511,512,528,529,575,576,577,578,624,625,675,721,722,728,729
%N A058075 Numbers k such that gcd(sigma(k), sigma(k+1)) = 1, where sigma(k) is sum of positive divisors of k.
%H A058075 Amiram Eldar, <a href="/A058075/b058075.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..3000 from Ivan Neretin)
%e A058075 8 is included because sigma(8) = 15 is relatively prime to sigma(9) = 13.
%t A058075 Select[Range@800, GCD @@ DivisorSigma[1, {#, # + 1}] == 1 &] (* _Ivan Neretin_, Jan 27 2017 *)
%t A058075 Drop[Position[Partition[DivisorSigma[1,Range[800]],2,1],_?(GCD@@#== 1&)]// Flatten,2] (* _Harvey P. Dale_, Jul 31 2019 *)
%o A058075 (PARI) lista(nn) = {for(n=1, nn, if (gcd(sigma(n), sigma(n+1)) == 1, print1(n, ", ")));} \\ _Michel Marcus_, May 19 2014
%Y A058075 Cf. A058074.
%K A058075 nonn
%O A058075 1,2
%A A058075 _Leroy Quet_, Nov 11 2000