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 A228490 #4 Oct 02 2013 14:29:00
%S A228490 3,7,55,59,65,75,93,133,137,141,249,277,313,365,375,387,391,435,471,
%T A228490 499,563,573,597,605,619,645,675,719,787,797,799,815,825,845,867,879,
%U A228490 919,937,957,971,1011,1013,1145,1217,1225,1243,1251,1271,1283,1311,1373
%N A228490 Numbers k for which prime(1) + ... + prime(k) = 2*prime(m) for some m.
%e A228490 a(1) = 3 because 2 + 3 + 5 = 2*prime(3) and p(3) = 5 is the least such prime summand.
%t A228490 z = 2800; f[n_] := Sum[Prime[k], {k, 1, n}]; p[n_] := If[PrimeQ[f[n]/2], 1, 0]; t = Table[p[n], {n, 1, z}]; Flatten[Position[t, 1]]
%Y A228490 Cf. A013916, A228491.
%K A228490 nonn
%O A228490 1,1
%A A228490 _Clark Kimberling_, Oct 01 2013