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!)
A215855 Number of simple labeled graphs on n nodes with exactly 5 connected components that are trees or cycles. 3
1, 15, 245, 3990, 70707, 1381695, 30015205, 724574235, 19353600409, 568456078190, 18238727824135, 635132015698180, 23864603640853943, 962474842863397305, 41472195692307932196, 1901422216588179732355, 92422276780875117660486, 4747285506511684927770980 (list; graph; refs; listen; history; text; internal format)
OFFSET

5,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 5..145

EXAMPLE

a(6) = 15: each graph has one 2-node tree and 4 1-node trees, and C(6,2) = 15.

MAPLE

T:= proc(n, k) option remember; `if`(k<0 or k>n, 0,

      `if`(n=0, 1, add(binomial(n-1, i)*T(n-1-i, k-1)*

      `if`(i<2, 1, i!/2 +(i+1)^(i-1)), i=0..n-k)))

    end:

a:= n-> T(n, 5):

seq(a(n), n=5..25);

CROSSREFS

Column k=5 of A215861.

The unlabeled version is A215985.

Sequence in context: A133199 A059760 A059615 * A163031 A065920 A273624

Adjacent sequences:  A215852 A215853 A215854 * A215856 A215857 A215858

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Aug 25 2012

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 27 06:03 EST 2020. Contains 332299 sequences. (Running on oeis4.)