A178008 - OEIS

%I #11 May 28 2016 10:22:55

%S 1,1,1,2,6,12,40,180,630,3360,22680,113400,831600,7484400,38918880,

%T 302702400,2918916000,20432412000,205837632000,2500927228800,

%U 21598916976000,263986763040000,3837961401120000,33774060329856000,431557437548160000,6658314750743040000

%N Number of permutations of 1..n with no element e[i>=2]<e[1+floor((i-2)/3)] (3-way heap).

%H Alois P. Heinz, <a href="/A178008/b178008.txt">Table of n, a(n) for n = 0..502</a>

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/D-ary_heap">D-ary heap</a>

%Y Simple 2-way heap A056971.

%Y Column k=3 of A273693.

%K nonn

%O 0,4

%A _R. H. Hardin_, May 17 2010

%E a(0), a(21)-a(25) from _Alois P. Heinz_, May 27 2016