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 A231624 #5 Nov 13 2013 15:04:08
%S A231624 1,2,3,7,8,9,13,14,15,17,21,25,27,31,32,33,37,39,43,44,45,49,50,51,53,
%T A231624 57,61,62,63,67,69,73,74,75,77,81,85,87,91,92,93,97,99,101,105,109,
%U A231624 111,115,116,117,121,122,123,127,128,129,133,134,135,137,141
%N A231624 Smallest sets of 3 consecutive deficient numbers in arithmetic progression. The initial deficient number is listed.
%H A231624 Shyam Sunder Gupta, <a href="/A231624/b231624.txt">Table of n, a(n) for n = 1..5000</a>
%e A231624 1, 2, 3 is the smallest set of 3 consecutive deficient numbers in arithmetic progression so 1 is in the list.
%t A231624 DefQ[n_] := DivisorSigma[1, n] < 2 n; m = 2; z1 = 2; cd = 1; a = {}; Do[If[DefQ[n], If[n - z1 == cd, m = m + 1; If[m > 2, AppendTo[a, n - 2*cd]], m = 2; cd = n - z1]; z1 = n], {n, 3, 1000000}]; a
%Y A231624 Cf. A005100, A231623, A228844.
%K A231624 nonn
%O A231624 1,2
%A A231624 _Shyam Sunder Gupta_, Nov 11 2013