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 A103289 #24 Dec 23 2020 04:11:22
%S A103289 1,4095,5775,5984,7424,11024,21735,21944,26144,27404,39375,43064,
%T A103289 49664,56924,58695,61424,69615,70784,76544,77175,79695,81080,81675,
%U A103289 82004,84524,84644,89775,91664,98175,103455,104895,106784,109395,111824
%N A103289 Numbers k such that both sigma(k) >= 2*k-1 and sigma(k+1) >= 2*(k+1)-1.
%C A103289 A004125(n) is less than A004125(n-1) and A004125(n+1) iff n belongs to A023196 but not to the current sequence.
%C A103289 Numbers k that both k and k+1 are in A103288.
%C A103289 Union of sequences A096399 and {2^m-1} for m in A103291.
%H A103289 Amiram Eldar, <a href="/A103289/b103289.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..2500 from Muniru A Asiru)
%p A103289 with(numtheory): a:=`if`(sigma(n)>=2*n-1 and sigma(n+1)>=2*(n+1)-1,n,NULL): seq(a(n),n=1..120000); # _Muniru A Asiru_, Jun 26 2018
%t A103289 Select[Range[120000], And[DivisorSigma[1, #] >= 2 #1 - 1, DivisorSigma[1, # + 1] >= 2 (#1 + 1) - 1] &] (* _Michael De Vlieger_, Jun 29 2018 *)
%o A103289 (PARI) for(i=1,1000000,if(sigma(i)>=2*i-1 && sigma(i+1)>=2*i+1, print1(i, ", ")));
%o A103289 (GAP) Filtered([1..120000],n->Sigma(n)>=2*n-1 and Sigma(n+1)>2*(n+1)-1); # _Muniru A Asiru_, Jun 26 2018
%Y A103289 Cf. A103288, A096399, A103291, A004125, A023196.
%K A103289 nonn
%O A103289 1,2
%A A103289 _Max Alekseyev_, Jan 28 2005