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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A183561 Number of partitions of n containing a clique of size 4. 12
1, 0, 1, 1, 3, 3, 5, 6, 10, 13, 20, 23, 35, 44, 61, 78, 103, 131, 174, 219, 285, 355, 456, 567, 721, 894, 1117, 1382, 1718, 2109, 2607, 3180, 3902, 4747, 5789, 7010, 8500, 10251, 12373, 14867, 17868, 21369, 25584, 30505, 36372, 43233 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,5

COMMENTS

All parts of a number partition with the same value form a clique. The size of a clique is the number of elements in the clique.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 4..1000

FORMULA

G.f.: (1-Product_{j>0} (1-x^(4*j)+x^(5*j))) / (Product_{j>0} (1-x^j)).

EXAMPLE

a(10) = 5, because 5 partitions of 10 contain (at least) one clique of size 4: [1,1,1,1,2,2,2], [1,1,2,2,2,2], [1,1,1,1,3,3], [1,1,1,1,2,4], [1,1,1,1,6].

MAPLE

b:= proc(n, i) option remember; `if`(n=0, [1, 0], `if`(i<1, [0, 0],

      add((l->`if`(j=4, [l[1]$2], l))(b(n-i*j, i-1)), j=0..n/i)))

    end:

a:= n-> (l-> l[2])(b(n, n)):

seq(a(n), n=4..50);

MATHEMATICA

max = 50; f = (1 - Product[1 - x^(4j) + x^(5j), {j, 1, max}])/Product[1 - x^j, {j, 1, max}]; s = Series[f, {x, 0, max}]; Drop[CoefficientList[s, x] , 4] (* Jean-Fran├žois Alcover, Oct 01 2014 *)

CROSSREFS

4th column of A183568. Cf. A000041, A183558, A183559, A183560, A183562, A183563, A183564, A183565, A183566, A183567.

Sequence in context: A241090 A091607 A276434 * A300183 A222704 A095950

Adjacent sequences:  A183558 A183559 A183560 * A183562 A183563 A183564

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jan 05 2011

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 26 03:09 EST 2020. Contains 332272 sequences. (Running on oeis4.)