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 A110175 #3 Mar 30 2012 17:22:40
%S A110175 6,30,49,81,91,95,115,121,155,187,205,210,221,243,254,259,287,298,299,
%T A110175 329,341,355,361,377,403,415,437,451,469,473,502,533,551,559,565,611,
%U A110175 625,629,649,655,662,667,674,679,685,703,713,731,737,746,767,779,781
%N A110175 Composite numbers n such that the equation phi(n)=phi(k)+phi(n-k) has no solution, where phi is Euler's totient function.
%C A110175 The only prime for which this equation has a solution is 3.
%t A110175 a[n_] := Select[Range[n-1], EulerPhi[n]==EulerPhi[n-# ]+EulerPhi[ # ]&]; t=Table[Length[a[n]], {n, 1000}]; Complement[Flatten[Position[t, 0]], Prime[Range[PrimePi[1000]]]]
%Y A110175 Cf. A110173 (least k such that phi(n)=phi(k)+phi(n-k)).
%K A110175 nonn
%O A110175 1,1
%A A110175 _T. D. Noe_, Jul 15 2005