The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A289717 The order of the semigroup of orientation-preserving or reserving partial transformations of n elements 1
 1, 2, 9, 64, 549, 4566, 34711, 243944, 1622025, 10402858, 65219931, 403119036, 2469129229, 15032191422, 91123985023, 550590488656, 3318118088721, 19953003487314, 119759533521571, 717624299625188, 4293868352394261, 25658433286034662, 153142720988745159, 913049836619756664 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Note the typo in corollary 27 of Umar (the 2nd equal sign in the equation in the first line should be a plus). LINKS V. H. Fernandes, G. M. S. Gomes, M. M. Jesus, Congruences on monoids of transformations preserving the orientation on a finite chain, J. Alg. 321 (3) (2009) 743-757, proposition 1.10 A. Umar, Combinatorial Results for Semigroups of Orientation-Preserving Partial Transformations, J. Int. Seq. 14 (2011) # 11.7.5, corollary 27, Tables 3.1-3.3. MAPLE # Table 3.3 of Umar A := proc(n, k)     if k = 0 then         1;     else         2*n*add(binomial(k-1, p-1)*binomial(n-1, p-1)*2^(n-p), p=1..k)-(n-1)*2^n-1-(k-1)*2^(n-1)*binomial(n, 2) ;     end if ; end proc: A289717 := proc(n)     add(A(n, k), k=0..n) ; end proc: CROSSREFS Sequence in context: A052513 A216839 A024720 * A094100 A185897 A067297 Adjacent sequences:  A289714 A289715 A289716 * A289718 A289719 A289720 KEYWORD nonn,easy AUTHOR R. J. Mathar, Sep 02 2017 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 August 3 07:58 EDT 2021. Contains 346435 sequences. (Running on oeis4.)