This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A053507 a(n) = binomial(n-1,2)*n^(n-3). 11
 0, 0, 1, 12, 150, 2160, 36015, 688128, 14880348, 360000000, 9646149645, 283787919360, 9098660462034, 315866083233792, 11806916748046875, 472877960873902080, 20205339187128111480, 917543123840934346752, 44131536275846038655193 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Number of connected unicyclic simple graphs on n labeled nodes such that the unique cycle has length 3. - Len Smiley, Nov 27 2001 Each simple graph (of this type) corresponds to exactly two 'functional digraphs' counted by A065513. REFERENCES R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Prop. 5.3.2. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..100 FORMULA E.g.f.: -1/3!*LambertW(-x)^3. - Vladeta Jovovic, Apr 07 2001 MATHEMATICA nn = 20; t = Sum[n^(n - 1) x^n/n!, {n, 1, nn}]; Drop[ Range[0, nn]! CoefficientList[Series[t^3/3!, {x, 0, nn}], x], 1]  (* Geoffrey Critzer, Jan 22 2012 *) PROG (MAGMA) [Binomial(n-1, 2)*n^(n-3):n in [1..20]]; // Vincenzo Librandi, Sep 22 2011 (PARI) for(n=1, 25, print1(binomial(n-1, 2)*n^(n-3), ", ")) \\ G. C. Greubel, Jan 18 2017 CROSSREFS Cf. A000169, A053506, A053508, A053509, A081133, A081132. Equals 2*A065513. A diagonal of A081130. Sequence in context: A056345 A264233 A068768 * A060917 A113358 A293153 Adjacent sequences:  A053504 A053505 A053506 * A053508 A053509 A053510 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 15 2000 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 17 19:15 EST 2018. Contains 317276 sequences. (Running on oeis4.)