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 A206804 #5 Mar 30 2012 18:58:12
%S A206804 1,4,13,26,49,78,121,188,264,370,498,638,804,1012,1265,1534,1854,2210,
%T A206804 2585,3020,3497,4040,4675,5358,6066,6826,7613,8456,9502,10608,11807,
%U A206804 13038,14434,15864,17399,19042,20759,22590,24538,26526,28719
%N A206804 (1/2)*A206803.
%t A206804 s[k_] := Prime[k + 1]; t[1] = 0;
%t A206804 p[n_] := Sum[s[k], {k, 1, n}];
%t A206804 c[n_] := n*s[n] - p[n]
%t A206804 t[n_] := t[n - 1] + (n - 1) s[n] - p[n - 1]
%t A206804 Table[c[n], {n, 2, 100}] (* A185382 *)
%t A206804 %/2 (* A206802 *)
%t A206804 Flatten[Table[t[n], {n, 2, 40}]] (* A206803 *)
%t A206804 %/2 (* A206804 *)
%Y A206804 Cf. A206803.
%K A206804 nonn
%O A206804 2,2
%A A206804 _Clark Kimberling_, Feb 13 2012