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

 

Logo

Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A032180 Number of ways to partition n labeled elements into 6 pie slices. 7

%I

%S 120,2520,31920,317520,2739240,21538440,158838240,1118557440,

%T 7612364760,50483192760,328191186960,2100689987760,13282470124680,

%U 83169792213480,516729467446080,3190281535536480,19596640721427000,119876382958008600

%N Number of ways to partition n labeled elements into 6 pie slices.

%C For n>=6, a(n) is equal to the number of functions f: {1,2,...,n-1}->{1,2,3,4,5,6} such that Im(f) contains 5 fixed elements. - Aleksandar M. Janjic and _Milan Janjic_, Feb 27 2007

%H Vincenzo Librandi, <a href="/A032180/b032180.txt">Table of n, a(n) for n = 6..1000</a>

%H C. G. Bower, <a href="/transforms2.html">Transforms (2)</a>

%H Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a>

%H <a href="/index/Ne#necklaces">Index entries for sequences related to necklaces</a>

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (21,-175,735,-1624,1764,-720).

%F "CIJ[ 6 ]" (necklace, indistinct, labeled, 6 parts) transform of 1, 1, 1, 1...

%F a(n) = 120*S(n, 6).

%F From _Emeric Deutsch_, May 02 2004: (Start)

%F a(n) = 5*2^(n-1) - 10*3^(n-1) + 10*4^(n-1) - 5^n + 6^(n-1) - 1.

%F a(n) = 120*A000770(n). (End)

%F G.f.: 120*x^6/((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)*(6*x-1)). - _Colin Barker_, Sep 03 2012

%F E.g.f.: (Sum_{k=0..6} (-1)^(6-k)*binomial(6,k)*exp(k*x))/6 with a(n) = 0 for n = 0..5. - _Wolfdieter Lang_, May 03 2017

%p with (combstruct):ZL:=[S, {S=Sequence(U, card=r), U=Set(Z, card>=1)}, labeled]: seq(count(subs(r=6, ZL), size=m)/6, m=6..21); # _Zerinvary Lajos_, Mar 08 2008

%t CoefficientList[Series[120/((x - 1) (2 x - 1) (3 x - 1) (4 x - 1) (5 x - 1) (6 x - 1)), {x, 0, 30}], x] (* _Vincenzo Librandi_, Oct 19 2013 *)

%t Table[120*Stirling2[n,6], {n,6,30}] (* _G. C. Greubel_, Nov 19 2017 *)

%o (MAGMA) [5*2^(n-1)-10*3^(n-1)+10*4^(n-1)-5^n+6^(n-1)-1: n in [6..30]]; // _Vincenzo Librandi_, Oct 19 2013

%o (PARI) for(n=6,30, print1(120*stirling(n,6,2), ", ")) \\ _G. C. Greubel_, Nov 19 2017

%Y Cf. A000770, A008277, A000225, A028243, A028244, A028245.

%K nonn,easy

%O 6,1

%A _Christian G. Bower_

%E More terms from _Vincenzo Librandi_ Oct 19 2013

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 December 14 12:28 EST 2018. Contains 318097 sequences. (Running on oeis4.)