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 A083251 #12 Jul 31 2017 03:35:05
%S A083251 2,48,72,80,112,176,208,272,304,368,464,496,592,656,688,752,848,944,
%T A083251 976,1072,1136,1168,1264,1328,1424,1552,1616,1648,1712,1744,1808,2032,
%U A083251 2096,2192,2224,2384,2416,2512,2608,2672,2768,2864,2896
%N A083251 Numbers n such that abs(A045763(n) - A073757(n)) = 2, i.e., signed difference of size of related and unrelated sets to n equals either 2 or -2.
%H A083251 Vincenzo Librandi, <a href="/A083251/b083251.txt">Table of n, a(n) for n = 1..1000</a>
%F A083251 a(n) = 8 * (A076274(n-1) + 1) for n > 3, as proved by Lawrence Sze. - _Ralf Stephan_, Nov 16 2004
%e A083251 For n=2896: d=10 divisors, r=1440 coprimes, u=1447 unrelated or n - u = r + d - 1 = 1449 related numbers to n; thus abs(1449 - 1447) = 2.
%t A083251 Do[r=EulerPhi[n]; d=DivisorSigma[0, n]; u=n-r-d+1; df=2*u-n; If[Equal[Abs[df], 2], Print[n(*, {d, r, u}*)]], {n, 1, 3000}]
%Y A083251 Cf. A000005, A000010, A045763, A073757, A083243-A083249, A083250.
%K A083251 nonn
%O A083251 1,1
%A A083251 _Labos Elemer_, May 07 2003