A271791 - OEIS

%I #5 Apr 14 2016 12:59:15

%S 0,1,15,129,891,5611,34213,208230,1285094,8108722,52540098,350375379,

%T 2407395908,17048774736,124435165429,935736058614,7246161094614,

%U 57749473020305,473358586652328,3987856784525223,34506189729577186,306454001139880689,2791593349164080381

%N Number of set partitions of [n] having exactly four pairs (m,m+1) such that m is in some block b and m+1 is in block b+1.

%H Alois P. Heinz, <a href="/A271791/b271791.txt">Table of n, a(n) for n = 4..300</a>

%e a(5) = 1: 1|2|3|4|5.

%e a(6) = 15: 12|3|4|5|6, 13|24|5|6, 1|23|4|5|6, 14|25|36, 1|24|35|6, 1|2|34|5|6, 15|26|3|4, 1|25|36|4, 1|2|35|46, 1|2|3|45|6, 16|2|3|4|5, 1|26|3|4|5, 1|2|36|4|5, 1|2|3|46|5, 1|2|3|4|56.

%Y Column k=4 of A185982.

%K nonn

%O 4,3

%A _Alois P. Heinz_, Apr 14 2016