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 A033691 #14 Nov 21 2013 13:11:19
%S A033691 4,8,12,20,24,32,40,52,60,72,84,100,112,128,144,164,180,200,220,244,
%T A033691 264,288,312,340,364,392,420,452,480,512,544,580,612,648,684,724,760,
%U A033691 800,840,884,924,968,1012,1060,1104,1152,1200,1252,1300,1352,1404,1460
%N A033691 Minimal number of vertices in 1-1 deficient regular graph where minimal degree is 1 and maximal degree is n.
%C A033691 A 1-1 deficient regular graph is one in which every vertex has the same degree as all of its neighbors except exactly one and its degree differs from the degree of this neighbor by exactly 1.
%H A033691 Vincenzo Librandi, <a href="/A033691/b033691.txt">Table of n, a(n) for n = 2..1000</a>
%F A033691 a(2*i) = 2*i*(i+1) i=1, 2, 3, ...; a(4*i+3) = 2*(i+1)*(4*i+4) i=0, 1, 2, ...; a(4*i+5) = 4*(2*i^2+6*i+5) i=1, 2, 3, ...
%F A033691 Empirical G.f.: -4*x^2*(x^5-2*x^4+x^3+1) / ((x-1)^3*(x+1)*(x^2+1)). [_Colin Barker_, Jan 15 2013]
%t A033691 a[n_?EvenQ] := n*(n+2)/2; a[n_ /; Mod[n, 4] == 3] := (n+1)^2/2; a[n_ /; Mod[n, 4] == 1] := (n^2 + 2*n + 5)/2; Table[a[n], {n, 2, 53}] (* _Jean-François Alcover_, Oct 10 2011 *)
%K A033691 easy,nice,nonn
%O A033691 2,1
%A A033691 Lisa R. Macon (lmacon(AT)valencia.cc.fl.us)
%E A033691 More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 23 2003