A271791 - OEIS

A271791

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.

0, 1, 15, 129, 891, 5611, 34213, 208230, 1285094, 8108722, 52540098, 350375379, 2407395908, 17048774736, 124435165429, 935736058614, 7246161094614, 57749473020305, 473358586652328, 3987856784525223, 34506189729577186, 306454001139880689, 2791593349164080381

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OFFSET

4,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 4..300

EXAMPLE

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

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.

CROSSREFS

Column k=4 of A185982.

Sequence in context: A056579 A294054 A156922 * A155656 A244878 A275101

Adjacent sequences: A271788 A271789 A271790 * A271792 A271793 A271794

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Apr 14 2016

STATUS

approved