login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A274870 Number of set partitions of [n] into exactly six blocks such that all odd elements are in blocks with an odd index and all even elements are in blocks with an even index. 2
1, 3, 22, 66, 311, 933, 3632, 10896, 38337, 115011, 381594, 1144782, 3664507, 10993521, 34404964, 103214892, 318365333, 955095999, 2918309966, 8754929898, 26585715663, 79757146989, 241208177496, 723624532488, 2182538747689, 6547616243067, 19713018571138 (list; graph; refs; listen; history; text; internal format)
OFFSET

6,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 6..1000

FORMULA

G.f.: -x^6/((x-1)*(3*x-1)*(2*x+1)*(2*x-1)*(x+1)*(6*x^2-1)*(2*x^2-1)).

EXAMPLE

a(7) = 3: 17|2|3|4|5|6, 1|2|37|4|5|6, 1|2|3|4|57|6.

a(8) = 22: 13|24|5|6|7|8, 15|24|3|6|7|8, 1|24|35|6|7|8, 15|26|3|4|7|8, 15|2|3|46|7|8, 1|26|35|4|7|8, 1|2|35|46|7|8, 17|26|3|4|5|8, 1|26|37|4|5|8, 1|26|3|4|57|8, 17|2|3|46|5|8, 1|2|37|46|5|8, 1|2|3|46|57|8, 17|28|3|4|5|6, 17|2|3|48|5|6, 17|2|3|4|5|68, 1|28|37|4|5|6, 1|2|37|48|5|6, 1|2|37|4|5|68, 1|28|3|4|57|6, 1|2|3|48|57|6, 1|2|3|4|57|68.

CROSSREFS

Column k=6 of A274537.

Sequence in context: A139272 A159345 A006532 * A178492 A005288 A143166

Adjacent sequences:  A274867 A274868 A274869 * A274871 A274872 A274873

KEYWORD

nonn,easy

AUTHOR

Alois P. Heinz, Jul 09 2016

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy .

Last modified February 21 04:43 EST 2018. Contains 299389 sequences. (Running on oeis4.)