This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A217436 Triangular array read by rows.  T(n,k) is the number of labeled relations on n elements with exactly k vertices of indegree and outdegree = 0. 0
 1, 1, 1, 13, 2, 1, 469, 39, 3, 1, 63577, 1876, 78, 4, 1, 33231721, 317885, 4690, 130, 5, 1, 68519123173, 199390326, 953655, 9380, 195, 6, 1, 562469619451069, 479633862211, 697866141, 2225195, 16415, 273, 7, 1, 18442242396353040817, 4499756955608552, 1918535448844, 1860976376, 4450390, 26264, 364, 8, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS Row sums = 2^(n^2). First column (k = 0) is A173403. Sum_{k=1,2,...,n} T(n,k)*k = A197927. LINKS FORMULA E.g.f.: exp(y*x)*A(x) where A(x) is the e.g.f. for A173403. EXAMPLE 1, 1, 1, 13, 2, 1, 469, 39, 3, 1, 63577, 1876, 78, 4, 1, 33231721, 317885, 4690, 130, 5, 1, 68519123173, 199390326, 953655, 9380, 195, 6, 1 MATHEMATICA nn=6; s=Sum[Sum[(-1)^k Binomial[n, k] 2^(n-k)^2, {k, 0, n}] x^n/n!, {n, 0, nn}]; Range[0, nn]! CoefficientList[Series[Exp[ y x] s, {x, 0, nn}], {x, y}] //Grid CROSSREFS Sequence in context: A010223 A010222 A086266 * A040166 A100395 A051310 Adjacent sequences:  A217433 A217434 A217435 * A217437 A217438 A217439 KEYWORD nonn,tabl AUTHOR Geoffrey Critzer, Oct 02 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.

Last modified October 14 03:58 EDT 2019. Contains 327995 sequences. (Running on oeis4.)