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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A215863 Number of simple labeled graphs on n+3 nodes with exactly n connected components that are trees or cycles. 2
0, 19, 135, 540, 1610, 3990, 8694, 17220, 31680, 54945, 90805, 144144, 221130, 329420, 478380, 679320, 945744, 1293615, 1741635, 2311540, 3028410, 3920994, 5022050, 6368700, 8002800, 9971325, 12326769, 15127560, 18438490, 22331160, 26884440, 32184944, 38327520 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..1000

FORMULA

G.f.: (6*x^2-2*x-19)*x/(x-1)^7.

a(n) = C(n+3,4)*(n^2+13*n+24)/2.

EXAMPLE

a(1) = 19:

.1-2.  .1-2.  .1 2.  .1-2.  .1-2.  .1 2.  .1 2.  .1 2.  .1-2.  .1-2.

.| |.  . X .  .|X|.  .|\ .  . /|.  . \|.  .|/ .  .| |.  .|  .  .| |.

.4-3.  .4-3.  .4.3.  .4.3.  .4.3.  .4-3.  .4-3.  .4-3.  .4-3.  .4.3.

.

.1-2.  .1 2.  .1-2.  .1-2.  .1-2.  .1 2.  .1 2.  .1 2.  .1 2.

.  |.  . X .  . / .  . \ .  . X .  .|/|.  . X|.  .|X .  .|\|.

.4-3.  .4-3.  .4-3.  .4-3.  .4.3.  .4.3.  .4.3.  .4.3.  .4.3.

MAPLE

a:= n-> binomial(n+3, 4)*(24+(13+n)*n)/2:

seq(a(n), n=0..40);

CROSSREFS

A diagonal of A215861.

Sequence in context: A041692 A078977 A085464 * A101090 A213122 A211092

Adjacent sequences:  A215860 A215861 A215862 * A215864 A215865 A215866

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 September 16 02:16 EDT 2019. Contains 327088 sequences. (Running on oeis4.)