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 A206715 #7 Sep 17 2013 05:24:23
%S A206715 5,10,15,20,30,40,45,60,65,75,80,85,90,95,105,120,125,130,135,150,160,
%T A206715 165,170,175,180,190,195,210,215,225,235,240,245,250,255,260,270,300,
%U A206715 320,325,330,335,340,350,360,365,380,390,420,430,450,455,470
%N A206715 Numbers matched to polynomials divisible by x^2+1.
%C A206715 Is this a duplicate of A131853?
%C A206715 The polynomials having coefficients in {0,1} are enumerated as in A206074. The sequence A206715 shows the numbers of those satisfying p(n,i)=0.
%t A206715 t = Table[IntegerDigits[n, 2], {n, 1, 3000}];
%t A206715 b[n_] := Reverse[Table[x^k, {k, 0, n}]]
%t A206715 p[n_, x_] := p[n, x] = t[[n]].b[-1 + Length[t[[n]]]]
%t A206715 TableForm[Table[{n, p[n, x], Factor[p[n, x]]},
%t A206715 {n, 1, 16}]]
%t A206715 u = {}; Do[n++; If[(p[n, x] /. x -> I) == 0,
%t A206715 AppendTo[u, n]], {n, 800}]
%t A206715 u (* A206715 *)
%t A206715 u/5 (* A206716 *)
%Y A206715 Cf. A131853, A206074, A206716.
%K A206715 nonn
%O A206715 1,1
%A A206715 _Clark Kimberling_, Feb 11 2012