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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A006957 Self-convolution of numbers of preferential arrangements. 5
1, 2, 7, 32, 185, 1310, 11067, 109148, 1234045, 15752858, 224169407, 3518636504, 60381131265, 1124390692886, 22577494959427, 486212633129300, 11177317486573445, 273173247028616594, 7072436847620016327 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

FORMULA

a(n) ~ n! / (log(2))^(n+1). - Vaclav Kotesovec, Nov 08 2014

G.f.: (Sum_{j>=0} j!*x^j / Product_{k=1..j} (1 - k*x))^2. - Ilya Gutkovskiy, Apr 06 2019

MAPLE

f:= proc(n) option remember; `if`(n<=1, 1,

      add(binomial(n, k) *f(n-k), k=1..n))

    end:

a:= n-> add(f(k)*f(n-k), k=0..n):

seq(a(n), n=0..25);  # Alois P. Heinz, Feb 02 2009

MATHEMATICA

t[n_] := Sum[StirlingS2[n, k]*k!, {k, 0, n}]; Table[Sum[t[k]*t[n-k], {k, 0, n}], {n, 0, 20}] (* Jean-François Alcover, Apr 09 2014, after Emanuele Munarini *)

PROG

(Maxima) t(n):=sum(stirling2(n, k)*k!, k, 0, n);

makelist(sum(t(k)*t(n-k), k, 0, n), n, 0, 20);

\\ Emanuele Munarini, Oct 02 2012

CROSSREFS

Cf. A000670, A217388, A217389.

Sequence in context: A000153 A006154 A000987 * A189780 A195983 A079265

Adjacent sequences:  A006954 A006955 A006956 * A006958 A006959 A006960

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Alois P. Heinz, Feb 02 2009

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 October 13 23:56 EDT 2019. Contains 327983 sequences. (Running on oeis4.)