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 A098205 #5 Oct 15 2013 22:32:34
%S A098205 0,9,70,539,6050,78819,1340212,25464389,585681476,16984763645,
%T A098205 526527673956,19481523937741,798742481449062,34345926702311515,
%U A098205 1614258555008643414,85555703415458103751,5047786501512028124790
%N A098205 A first order iteration: n-th term is obtained from (n-1)-th by adding n-th prime and then multiplying by the n-th prime; initial value is 0.
%C A098205 Difference between sequences generated by this recursion with iv=1[A098206] and iv=0[A098205] provides A070826, i.e. half of n-th primorial number. Analogous recursion is A019461.
%F A098205 a[n]=(a[n-1]+p[n])*p[n], a[0]=0.
%e A098205 a[4]=(70+p[4])*p[4]=(70+7)*7=490+49=539=
%t A098205 f[x_] :=(f[x-1]+Prime[x])*Prime[x];f[1]=0; Table[f[w], {w, 1, 25}]
%Y A098205 Cf. A098206, A070826, A019461.
%K A098205 nonn
%O A098205 1,2
%A A098205 _Labos Elemer_, Oct 19 2004