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A168658 a(n) = ceiling(n^n/2). 16
1, 1, 2, 14, 128, 1563, 23328, 411772, 8388608, 193710245, 5000000000, 142655835306, 4458050224128, 151437553296127, 5556003412779008, 218946945190429688, 9223372036854775808, 413620130943168382089 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Number of functions of [n] to [n] (endofunctions of degree n) up to complement to n+1.

There is only one function, and only when n=2k-1 is odd, fixed by n+1-complement, the constant function with value k.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..300

FORMULA

a(n) = ceiling(A000312(n)/2).

EXAMPLE

Ceiling(6^6/2) = 23328.

MATHEMATICA

Join[{1}, Table[Ceiling[n^n/2], {n, 1, 25}]] (* G. C. Greubel, Jul 28 2016 *)

PROG

(Sage) [ceil(n^n/2) for n in xrange(0, 21)]#

(MAGMA)[Ceiling(n^n/2): n in [0..20]]; // Vincenzo Librandi, Aug 29 2011

(PARI) a(n) = ceil(n^n/2); \\ Michel Marcus, Feb 18 2016

CROSSREFS

Cf. A000312 (all endofunctions of degree n)

Cf. A057065 (floor of n^n / 2).

Sequence in context: A216595 A155650 A258389 * A235347 A235352 A146971

Adjacent sequences:  A168655 A168656 A168657 * A168659 A168660 A168661

KEYWORD

nonn,easy

AUTHOR

Zerinvary Lajos, Dec 02 2009

STATUS

approved

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Last modified February 19 14:54 EST 2018. Contains 299334 sequences. (Running on oeis4.)