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 A095817 #12 Aug 31 2018 20:03:44
%S A095817 1,1,2,6,22,114,692,4884,39318,355490,3567292,39345804,473148014,
%T A095817 6161310442,86376341412,1297099489668,20772929663254,353415786538434,
%U A095817 6365693021157116,121016486728717740,2421505946364174606,50873034832373299370,1119617627206173146308
%N A095817 Number of permutations of 1..n with no four elements in correct or reverse order.
%C A095817 For no k do either of the subsequences k(k+1)(k+2)(k+3) or (k+3)(k+2)(k+1)k occur in any permutation.
%H A095817 D. M. Jackson and R. C. Read, <a href="http://gdz.sub.uni-goettingen.de/dms/load/img/?PID=GDZPPN002031183">A note on permutations without runs of given length</a>, Aequationes Math. 17 (1978), no. 2-3, 336-343.
%F A095817 G.f.: Sum_{n>=0} n!*((2*x^m-x^(m+1)-x)/(x^m-1))^n where m = 4. - Ivana Jovovic ( ivana121(AT)EUnet.yu ), Nov 11 2007
%o A095817 (PARI) seq(n)={my(m=4); Vec(sum(k=0, n, k!*((2*x^m-x^(m+1)-x)/(x^m-1) + O(x*x^n))^k))} \\ _Andrew Howroyd_, Aug 31 2018
%Y A095817 Cf. A002464, A095816, A095818.
%K A095817 nonn
%O A095817 0,3
%A A095817 _Jonas Wallgren_, Jun 08 2004
%E A095817 More terms from Ivana Jovovic ( ivana121(AT)EUnet.yu ), Nov 11 2007
%E A095817 a(0)=1 prepended and terms a(20) and beyond from _Andrew Howroyd_, Aug 31 2018