login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A250119 Triangle read by rows: T(n,m) (n >= 1, 1 <= m <= n) = number of set partitions of [n], avoiding 123454, with m blocks. 3

%I #28 Feb 27 2020 10:11:16

%S 1,1,1,1,3,1,1,7,6,1,1,15,25,10,1,1,31,90,65,14,1,1,63,301,350,121,18,

%T 1,1,127,966,1701,834,193,22,1,1,255,3025,7770,5037,1606,281,26,1,1,

%U 511,9330,34105,27918,11461,2730,385,30,1,1,1023,28501,145750,145777,73762,22381,4270,505,34,1

%N Triangle read by rows: T(n,m) (n >= 1, 1 <= m <= n) = number of set partitions of [n], avoiding 123454, with m blocks.

%H Lars Blomberg, <a href="/A250119/b250119.txt">Table of n, a(n) for n = 1..5050</a> (The first 100 rows.)

%H Harry Crane, <a href="https://ajc.maths.uq.edu.au/pdf/61/ajc_v61_p057.pdf">Left-right arrangements, set partitions, and pattern avoidance</a>, Australasian Journal of Combinatorics, 61(1) (2015), 57-72.

%e Triangle begins:

%e 1;

%e 1, 1;

%e 1, 3, 1;

%e 1, 7, 6, 1;

%e 1, 15, 25, 10, 1;

%e 1, 31, 90, 65, 14, 1;

%e 1, 63, 301, 350, 121, 18, 1;

%e 1, 127, 966, 1701, 834, 193, 22, 1;

%e 1, 255, 3025, 7770, 5037, 1606, 281, 26, 1;

%e 1, 511, 9330, 34105, 27918, 11461, 2730, 385, 30, 1;

%e 1, 1023, 28501, 145750, 145777, 73762, 22381, 4270, 505, 34, 1;

%e ...

%Y Cf. A112857, A250118. A163942 is a diagonal.

%K nonn,tabl

%O 1,5

%A _N. J. A. Sloane_, Nov 25 2014

%E a(46)-a(66) from _Lars Blomberg_, Aug 17 2017

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)