The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A318398 Number of triples of set partitions of {1,2,...,n} whose meet is {{1},{2},...,{n}}. 2

%I

%S 1,7,103,2707,110857,6517129,521167549,54510591469,7235648605909,

%T 1190181847444189,237953165658759679,56905537750421669449,

%U 16059682765076576965879,5287171379685771887014489,2010360123437921314268936809,875173620070717892287441139989

%N Number of triples of set partitions of {1,2,...,n} whose meet is {{1},{2},...,{n}}.

%F a(n) = Sum_{k = 0...n} s(n,k) B(k)^3 where s = A048994 and B = A000110.

%e The a(2) = 7 triples:

%e {{1},{2}} {{1},{2}} {{1},{2}}

%e {{1},{2}} {{1},{2}} {{1,2}}

%e {{1},{2}} {{1,2}} {{1},{2}}

%e {{1},{2}} {{1,2}} {{1,2}}

%e {{1,2}} {{1},{2}} {{1},{2}}

%e {{1,2}} {{1},{2}} {{1,2}}

%e {{1,2}} {{1,2}} {{1},{2}}

%t Table[Sum[StirlingS1[n,k]*BellB[k]^3,{k,0,n}],{n,10}]

%Y Cf. A000110, A000258, A001247, A008277, A048994, A059849, A060639, A181939, A318389, A318391, A318393, A318399.

%K nonn

%O 1,2

%A _Gus Wiseman_, Aug 25 2018

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 25 04:15 EDT 2021. Contains 345452 sequences. (Running on oeis4.)