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 A201156 #8 Mar 31 2012 10:24:06
%S A201156 1,3,10,11,56,57,400,401,402,403,4434,4435,57656,57657,57658,57659,
%T A201156 980204,980205,18623896,18623897,18623898,18623899,428349678,
%U A201156 428349679,428349680,428349681,428349682,428349683,12422140808,12422140809,385086365080,385086365081
%N A201156 Row sums of triangle A201146.
%C A201156 a(n) = a(n-1) + 1 if and only if n is a composite number.
%H A201156 Arkadiusz Wesolowski, <a href="/A201156/b201156.txt">Table of n, a(n) for n = 1..502</a>
%t A201156 Table[Sum[Product[Prime[i], {i, PrimePi[n]}]/Product[Prime[i], {i, PrimePi[k]}], {k, n}], {n, 32}]
%Y A201156 Cf. A201146.
%K A201156 nonn
%O A201156 1,2
%A A201156 _Arkadiusz Wesolowski_, Nov 27 2011