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 A108957 #8 Sep 21 2019 08:25:57 %S A108957 2,3,4,5,6,9,11,12,15,17,18,23,27,33,35,39,45,47,51,53,54,59,63,65,66, %T A108957 69,75,77,83,87,93,95,99,107,111,117,119,123,125,126,129,131,135,137, %U A108957 138,143,147,149,150,153,155,159,165,167,171,173,174,179,183,185,186 %N A108957 Values of n such that n - 2^k is deficient for all 1 <= 2^k < n. %C A108957 Conjectures: a. Sequence is infinite. b. There are infinitely many consecutive pairs, such as (5:6), (11:12), (17:18), (53:54), ... (204005:204006). %H A108957 Amiram Eldar, <a href="/A108957/b108957.txt">Table of n, a(n) for n = 1..10000</a> %e A108957 53 is a term because 52, 51, 49, 45, 37 and 21 are all deficient numbers. %t A108957 aQ[n_] := AllTrue[n - 2^Range[0, Floor[Log2[n]]], # == 0 || DivisorSigma[1, #] < 2 # &]; Select[Range[2, 186], aQ] (* _Amiram Eldar_, Sep 21 2019 *) %Y A108957 Cf. A005100, A039669. %K A108957 easy,nonn %O A108957 1,1 %A A108957 _Jason Earls_, Jul 22 2005