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 A001684 M1693 N0669 #22 Jun 20 2017 12:24:02
%S A001684 1,1,1,1,2,6,30,390,32370,81022110,79098077953830,
%T A001684 2499603048957386233742790,
%U A001684 6399996109983215106481566902449146981585570,1296147136591533261616288032775924136752630487513536584267056282299509616710
%N A001684 From a continued fraction.
%D A001684 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A001684 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A001684 John Cerkan, <a href="/A001684/b001684.txt">Table of n, a(n) for n = 0..17</a>
%H A001684 V. C. Harris, <a href="http://www.jstor.org/stable/2309559">Another proof of the infinitude of primes</a>, Amer. Math. Monthly, 63 (1956), 711.
%F A001684 a(0) = a(1) = a(2) = 1, a(n) = Product_{k=0..n-3} A001685(k) for n >= 3. - _Sean A. Irvine_, Nov 13 2012
%K A001684 nonn
%O A001684 0,5
%A A001684 _N. J. A. Sloane_
%E A001684 One more term from _Sean A. Irvine_, Nov 13 2012