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A070960 a(1) = 1; a(n) = n!*(3/2) for n>=2. 10
1, 3, 9, 36, 180, 1080, 7560, 60480, 544320, 5443200, 59875200, 718502400, 9340531200, 130767436800, 1961511552000, 31384184832000, 533531142144000, 9603560558592000, 182467650613248000, 3649353012264960000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Let g be a permutation of [1..n] having, say, j_i cycles of length i, with Sum_i i*j_i = n; sequence gives Sum_{g} Sum_{i} (j_1 + j_2). - N. J. A. Sloane, Jul 22 2009

a(n) is the greatest integer that can be obtained from the integers {1, 2, 3, ..., n} using each number at most once and the operators +, -, *, /.

a(n) = A245334(n,n-2), n > 1. - Reinhard Zumkeller, Aug 31 2014

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..400

Index entries for similar sequences

FORMULA

E.g.f.: x*(2+x)/(1-x)/2. - Vladeta Jovovic, Dec 15 2002

EXAMPLE

a(5) = 180 because the greatest number we can obtain using 1, 2, 3, 4, 5 is 180 which is (1+2)*3*4*5.

MATHEMATICA

s=3; lst={1, s}; Do[s+=n*s+s; AppendTo[lst, s], {n, 1, 5!, 1}]; lst (* Vladimir Joseph Stephan Orlovsky, Nov 08 2008 *)

PROG

(Haskell)

a070960 n = if n == 1 then 1 else 3 * a000142 n `div` 2

a070960_list = map (flip div 2) fs where fs = 3 : zipWith (*) [2..] fs

-- Reinhard Zumkeller, Aug 31 2014

CROSSREFS

Cf. A000142, A060315.

Cf. A245334.

Sequence in context: A144352 A107895 A237653 * A030834 A030893 A030936

Adjacent sequences:  A070957 A070958 A070959 * A070961 A070962 A070963

KEYWORD

easy,nonn

AUTHOR

Koksal Karakus (karakusk(AT)hotmail.com), May 24 2002

EXTENSIONS

Edited by N. J. A. Sloane, Jul 22 2009

STATUS

approved

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Last modified October 17 11:41 EDT 2019. Contains 328108 sequences. (Running on oeis4.)