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 A382875 #10 Jun 30 2025 04:29:09
%S A382875 0,3,6,7,9,12,14,15,18,21,24,27,28,30,31,33,35,36,39,42,45,48,49,51,
%T A382875 54,56,57,60,62,63,66,69,70,72,75,77,78,81,84,87,90,91,93,96,98,99,
%U A382875 102,105,108,111,112,114,117,119,120,123,124,126,127,129,132,133,135,138,140
%N A382875 Numbers which are a multiple of 2^k - 1 for some k > 1.
%C A382875 The asymptotic density of this sequence is Sum_{s subset of A000225 \ {0, 1}} (-1)^(card(s)+1)/LCM(s) = 0.45169 ... . - _Amiram Eldar_, Jun 30 2025
%t A382875 nmax=140; Complement[Range[0,nmax], Position[Table[DivisorSum[n, 1 &, IntegerQ@ Log2[# + 1] &], {n, nmax}], 1][[All, 1]]] (* after _Michael De Vlieger_, Jun 11 2018 in A161790 *)
%o A382875 (PARI) isok(k) = if(k == 0, 1, forstep(i = logint(k+1, 2), 2, -1, if(k % (2^i-1) == 0, return(1))); 0); \\ _Amiram Eldar_, Jun 30 2025
%Y A382875 Complement of A161790 in A001477.
%Y A382875 Cf. A000225, A161788, A161789.
%K A382875 nonn
%O A382875 1,2
%A A382875 _Stefano Spezia_, Apr 07 2025