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 A248470 #31 Nov 14 2014 13:06:30
%S A248470 1,2,1,2,1,2,3,2,1,1,6,38,167,2095,1,2030,3,15,21,138,263,2,57,1266,
%T A248470 3470,7,145742,10,4682335,110,38,618,366,83,3343,3279,206555,215547,
%U A248470 489378,52010,21,5127,11,54663,6203,5041187,194,63038411,407039,7602,2,2474
%N A248470 Put a [+] b = A(A(a) + A(b)), where A = A007913; a(n) is the [+]-sum of binomial(n,i), i=0,...,n.
%C A248470 By definition, all terms are squarefree (A005117).
%e A248470 For n=4, we have binomials: 1,4,6,4,1.
%e A248470 To obtain a(4), we form the sums 1[+]4 = 1[+]1 = 2; 2[+]6 = 2; 2[+]4 = 2[+]1 = 3; 3[+]1=1. So a(4)=1.
%t A248470 a7913[n_]:=a7913[n]=Times@@(#[[1]]^Mod[#[[2]],2])&[Transpose[FactorInteger[n]]];
%t A248470 ab[x_,y_]:=ab[x,y]=a7913[a7913[x]+a7913[y]];
%t A248470 Table[Fold[ab,First[#],Rest[#]]&[Binomial[n,#]&[Range[0,n]]],{n,0,50}] (* _Peter J. C. Moses_, Oct 27 2014 *)
%o A248470 (PARI) a(n) = {s = 0; for (i=0, n, s = core(core(binomial(n, i)) + core(s))); s;} \\ _Michel Marcus_, Nov 14 2014
%Y A248470 Cf. A005117, A007318, A007913.
%K A248470 nonn
%O A248470 0,2
%A A248470 _Vladimir Shevelev_, Oct 27 2014
%E A248470 More terms from _Peter J. C. Moses_, Oct 27 2014