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A289715 The order of the semigroup of orientation-preserving full transformations on n elements. 1
1, 4, 24, 128, 610, 2742, 11970, 51424, 218718, 923690, 3879766, 16224804, 67603744, 280816018, 1163381190, 4808642880, 19835652598, 81676217394, 335780005758, 1378465287820, 5651707681200, 23145088600458, 94684453366894, 386971244196648, 1580132580471300, 6446940928324702 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..26.

A. Umar, Combinatorial Results for Semigroups of Orientation-Preserving Partial Transformations, J. Int. Seq. 14 (2011) # 11.7.5, corollary 17, table 2.4, table 2.5.

FORMULA

a(n) = A002457(n-1)-A002378(n-1).

(n-1)*(3*n-10)*a(n) +6*(-3*n^2+12*n-8)*a(n-1) +3*(9*n^2-35*n+32)*a(n-2) -2*(3*n-4)*(2*n-5)*a(n-3)=0.

MAPLE

A289715 := proc(n)

    n/2*binomial(2*n, n)-n*(n-1) ;

end proc:

CROSSREFS

Sequence in context: A098224 A024049 A103455 * A174443 A180222 A192070

Adjacent sequences:  A289712 A289713 A289714 * A289716 A289717 A289718

KEYWORD

nonn,easy

AUTHOR

R. J. Mathar, Sep 02 2017

STATUS

approved

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Last modified April 8 14:52 EDT 2020. Contains 333314 sequences. (Running on oeis4.)