A178009 - OEIS

%I #14 May 28 2016 10:22:39

%S 1,1,1,2,6,24,60,240,1260,8064,36288,241920,1995840,19160064,

%T 124540416,1162377216,13076743680,167382319104,1422749712384,

%U 17072996548608,243290200817664,3892643213082624,34060628114472960,428190753439088640,6463004184721244160

%N Number of permutations of 1..n with no element e[i>=2]<e[1+floor((i-2)/4)] (4-way heap).

%H Alois P. Heinz, <a href="/A178009/b178009.txt">Table of n, a(n) for n = 0..491</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=4 of A273693.

%K nonn

%O 0,4

%A _R. H. Hardin_, May 17 2010

%E a(0), a(20)-a(24) from _Alois P. Heinz_, May 27 2016