%I
%S 1,2,6,24,116,672,4536,34944,302896,2916992,30899616,357080064,
%T 4470310976,60269056512,870591770496,13414154256384,219604379097856,
%U 3806644208863232,69650568655858176,1341477655028219904,27128858382696129536,574755293400886321152
%N Number of permutations of 1..n avoiding adjacent step pattern up, down, down, down.
%H Alois P. Heinz, <a href="/A177518/b177518.txt">Table of n, a(n) for n = 1..175</a>
%F a(n) ~ c * n! / r^n, where r = 1.03841563726655630653502212237531835609230623619708108964... is the root of the equation cos(r)  sin(r) + exp(r) = 0, and c = 1.1718801964367046779834894478269895859267745270209175... .  _Vaclav Kotesovec_, Aug 21 2014
%Y Column k=0 of A242820.
%Y Columns k=8,14 of A242784.
%K nonn
%O 1,2
%A _R. H. Hardin_, May 10 2010
%E a(18)a(22) from _Alois P. Heinz_, Oct 06 2013
