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 A003314 Binary entropy function: a(1)=0; for n > 1, a(n) = n + min { a(k)+a(n-k) : 1 <= k <= n-1 }. (Formerly M1345) 13

%I M1345

%S 0,2,5,8,12,16,20,24,29,34,39,44,49,54,59,64,70,76,82,88,94,100,106,

%T 112,118,124,130,136,142,148,154,160,167,174,181,188,195,202,209,216,

%U 223,230,237,244,251,258,265,272,279,286,293,300,307,314,321,328,335

%N Binary entropy function: a(1)=0; for n > 1, a(n) = n + min { a(k)+a(n-k) : 1 <= k <= n-1 }.

%C Morris gives many other interesting properties of this function.

%C a(n) is a convex function of n. (See the Morris reference.)

%D D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, Vol. 3, Sect 5.4.9, Eq. (19). p. 374.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Indranil Ghosh, <a href="/A003314/b003314.txt">Table of n, a(n) for n = 1..32768</a> (terms 1..1000 from T. D. Noe)

%H Mareike Fischer, <a href="https://arxiv.org/abs/1801.10418">Extremal values of the Sackin balance index for rooted binary trees</a>, arXiv:1801.10418 [q-bio.PE], 2018.

%H D Chistikov, S Iván, A Lubiw, J Shallit, <a href="https://arxiv.org/abs/1509.07588">Fractional coverings, greedy coverings, and rectifier networks</a>, arXiv preprint arXiv:1509.07588 [cs.CC], 2015-2016.

%H Hsien-Kuei Hwang, S. Janson, T. H. Tsai, <a href="http://140.109.74.92/hk/wp-content/files/2016/12/aat-hhrr-1.pdf">Exact and asymptotic solutions of the recurrence f(n) = f(floor(n/2)) + f(ceiling(n/2)) + g(n): theory and applications</a>, Preprint 2016.

%H Hsien-Kuei Hwang, S. Janson, T. H. Tsai, <a href="https://doi.org/10.1145/3127585">Exact and Asymptotic Solutions of a Divide-and-Conquer Recurrence Dividing at Half: Theory and Applications</a>, ACM Transactions on Algorithms, 13:4 (2017), #47; DOI: 10.1145/3127585.

%H D. Knuth, <a href="/A003063/a003063.pdf">Letter to N. J. A. Sloane, date unknown</a>

%H R. Morris, <a href="http://dx.doi.org/10.1137/0117001">Some theorems on sorting</a>, SIAM J. Appl. Math., 17 (1969), 1-6.

%F a(1) = 0; a(n) = n + a([n/2]) + a(n-[n/2]). (See the Morris reference.)

%F a(n) = A001855(n)+n-1. - _Michael Somos_ Feb 07 2004

%F a(n) = n + a(floor(n/2)) + a(ceiling(n/2)) = n*floor(log_2(4n))-2^floor(log_2(2n)) = A033156(n) - n = n*A070941(n) - A062383(n). - _Henry Bottomley_, Jul 03 2002

%F a(1) = 0 and for n>1: a(n) = a(n-1) + A070941(2*n-1). Also a(n) = A123753(n-1) - 1. - _Reinhard Zumkeller_, Oct 12 2006

%F a(n) = A123753(n-1) - 1. - _Peter Luschny_, Nov 30 2017

%e a(6) = 6 + min {1+12, 2+8, 5+5} = 6 + 10 = 16.

%p A003314 := proc(n) local i,j; option remember; if n<=2 then n elif n=3 then 5 else j := 10^10; for i from 1 to n-1 do if A003314(i)+A003314(n-i) < j then j := A003314(i)+A003314(n-i); fi; od; n+j; fi; end;

%t a[1] = 0; a[n_] := If[OddQ[n], n + a[(n-1)/2 + 1] + a[(n-1)/2], 2*(n/2 + a[n/2])];

%t Table[a[n], {n, 1, 57}] (* _Jean-François Alcover_, Oct 15 2012 *)

%t a[n_] := n + n IntegerLength[n, 2] - 2^IntegerLength[n, 2];

%t Table[a[n], {n, 1, 57}] (* _Peter Luschny_, Dec 02 2017 *)

%o (PARI) a(n)=if(n<2,0,n+a(n\2)+a((n+1)\2))

%o (PARI) a(n)=local(m);if(n<2,0,m=length(binary(n-1));n*m-2^m+n)

%o a003314 n = a003314_list !! (n-1)

%o a003314_list = 0 : f [0] [2..] where

%o f vs (w:ws) = y : f (y:vs) ws where

%o y = w + minimum (zipWith (+) vs \$ reverse vs)

%o -- _Reinhard Zumkeller_, Aug 13 2013

%o (Python)

%o def A003314(n):

%o ....return n*int(math.log(4*n,2))-2**int(math.log(2*n,2)) # _Indranil Ghosh_, Feb 03 2017

%o (Python)

%o def A003314(n):

%o s, i, z = n-1, n-1, 1

%o while 0 <= i: s += i; i -= z; z += z

%o return s

%o print([A003314(n) for n in range(1, 58)]) # _Peter Luschny_, Nov 30 2017

%Y Cf. A054248, A097071, A123753.

%K nonn,easy,nice

%O 1,2

%A _N. J. A. Sloane_

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Last modified May 23 03:32 EDT 2018. Contains 304449 sequences. (Running on oeis4.)