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 A071258 #6 Mar 26 2014 12:24:16
%S A071258 4,9,28,57,115,231,694,1389,2779,5559,16678,33357,66715,133431,400294,
%T A071258 800589,1601179,3202359,9607078,19214157,38428315,76856631,153713263,
%U A071258 307426527,614853055,1229706111,3689118334,7378236669,14756473339
%N A071258 a(1) = 4; a(n) = smallest composite number of form k*a(n-1) + 1 with k > 1.
%H A071258 Harvey P. Dale, <a href="/A071258/b071258.txt">Table of n, a(n) for n = 0..1000</a>
%t A071258 nxt[n_]:=Module[{k=2},While[PrimeQ[k*n+1],k++];k*n+1]; NestList[nxt,4,30] (* _Harvey P. Dale_, Mar 26 2014 *)
%Y A071258 Cf. A061766, A061092, A059411.
%K A071258 nonn
%O A071258 0,1
%A A071258 _Amarnath Murthy_, May 30 2002
%E A071258 More terms from _Vladeta Jovovic_, Jun 03 2002