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 A038712 Let k be the exponent of highest power of 2 dividing n (A007814); a(n) = 2^(k+1)-1. 62
 1, 3, 1, 7, 1, 3, 1, 15, 1, 3, 1, 7, 1, 3, 1, 31, 1, 3, 1, 7, 1, 3, 1, 15, 1, 3, 1, 7, 1, 3, 1, 63, 1, 3, 1, 7, 1, 3, 1, 15, 1, 3, 1, 7, 1, 3, 1, 31, 1, 3, 1, 7, 1, 3, 1, 15, 1, 3, 1, 7, 1, 3, 1, 127, 1, 3, 1, 7, 1, 3, 1, 15, 1, 3, 1, 7, 1, 3, 1, 31, 1, 3, 1, 7, 1, 3, 1, 15, 1, 3, 1, 7, 1, 3, 1, 63, 1, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS n XOR n-1, i.e., nim-sum of a pair of consecutive numbers. Denominator of quotient sigma(2*n)/sigma(n). - Labos Elemer, Nov 04 2003 a(n) = the Towers of Hanoi disc moved at the n-th move, using standard moves with discs labeled (1, 3, 7, 15, ...) starting from top (smallest = 1). - Gary W. Adamson, Oct 26 2009 Equals row sums of triangle A168312. - Gary W. Adamson, Nov 22 2009 In the binary expansion of n, delete everything left of the rightmost 1 bit, and set all bits to the right of it. - Ralf Stephan, Aug 22 2013 Every finite sequence of positive integers summing to n may be termwise dominated by a subsequence of the first n values in this sequence [see Bannister et al., 2013]. - David Eppstein, Aug 31 2013 Sum of powers of 2 dividing n. - Omar E. Pol, Aug 18 2019 Given the binary expansion of (n-1) as {b[k-1], b[k-2], ..., b[2], b[1], b[0]}, then the binary expansion of a(n) is {bitand(b[k-1], b[k-2], ..., b[2], b[1], b[0]), bitand(b[k-2], ..., b[2], b[1], b[0]), ..., bitand(b[2], b[1], b[0]), bitand(b[1], b[0]), b[0], 1}. Recursively stated - 0th bit (L.S.B) of a(n), a(n)[0] = 1, a(n)[i] = bitand(a(n)[i-1], (n-1)[i-1]), where n[i] = i-th bit in the binary expansion of n. - Chinmaya Dash, Jun 27 2020 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 M. J. Bannister, Z. Cheng, W. E. Devanny, and D. Eppstein, Superpatterns and universal point sets, 21st Int. Symp. Graph Drawing, 2013, arXiv:1308.0403 [cs.CG], 2013. Klaus Brockhaus, Illustration of A038712 and A080277. David Eppstein, 1317131 and majorization by subsequences. Fabrizio Frati, M. Patrignani, and V. Roselli, LR-Drawings of Ordered Rooted Binary Trees and Near-Linear Area Drawings of Outerplanar Graphs, arXiv preprint arXiv:1610.02841 [cs.CG], 2016. Malgorzata J. Krawczyk, Paweł Oświęcimka, and Krzysztof Kułakowski, Ordered Avalanches on the Bethe Lattice, Entropy, Vol. 21, (2019) 968. Ralf Stephan, Table of generating functions. Ralf Stephan, Divide-and-conquer generating functions. I. Elementary sequences, arXiv:math/0307027 [math.CO], 2003. FORMULA a(n) = A110654(n-1) XOR A008619(n). - Reinhard Zumkeller, Feb 05 2007 a(n) = 2^A001511(n) - 1 = 2*A006519(n) - 1 = 2^(A007814(n)+1) - 1. Multiplicative with a(2^e) = 2^(e+1)-1, a(p^e) = 1, p > 2. - Vladeta Jovovic, Nov 06 2001; corrected by Jianing Song, Aug 03 2018 Sum_{n>0} a(n)*x^n/(1+x^n) = Sum_{n>0} x^n/(1-x^n). Inverse Moebius transform of A048298. - Vladeta Jovovic, Jan 02 2003 From Ralf Stephan, Jun 15 2003: (Start) G.f.: Sum_{k>=0} 2^k*x^2^k/(1 - x^2^k). a(2*n+1) = 1, a(2*n) = 2*a(n)+1. (End) Equals A130093 * [1, 2, 3, ...]. - Gary W. Adamson, May 13 2007 Sum_{i=1..n} (-1)^A000120(n-i)*a(i) = (-1)^(A000120(n)-1)*n. - Vladimir Shevelev, Mar 17 2009 Dirichlet g.f.: zeta(s)/(1 - 2^(1-s)). - R. J. Mathar, Mar 10 2011 a(n) = A086799(2*n) - 2*n. - Reinhard Zumkeller, Aug 07 2011 a((2*n-1)*2^p) = 2^(p+1)-1, p >= 0. - Johannes W. Meijer, Feb 01 2013 a(n) = A000225(A001511(n)). - Omar E. Pol, Aug 31 2013 a(n) = A000203(n)/A000593(n). - Ivan N. Ianakiev and Omar E. Pol, Dec 14 2017 L.g.f.: -log(Product_{k>=0} (1 - x^(2^k))) = Sum_{n>=1} a(n)*x^n/n. - Ilya Gutkovskiy, Mar 15 2018 a(n) = 2^(1 + (A183063(n)/A001227(n))) - 1. - Omar E. Pol, Nov 06 2018 a(n) = sigma(n)/(sigma(2*n) - 2*sigma(n)) = 3*sigma(n)/(sigma(4*n) - 4*sigma(n)) = 7*sigma(n)/(sigma(8*n) - 8*sigma(n)), where sigma(n) = A000203(n). - Peter Bala, Jun 10 2022 Sum_{k=1..n} a(k) ~ n*log_2(n) + (1/2 + (gamma - 1)/log(2))*n, where gamma is Euler's constant (A001620). - Amiram Eldar, Nov 24 2022 EXAMPLE a(6) = 3 because 110 XOR 101 = 11 base 2 = 3. From Omar E. Pol, Aug 18 2019: (Start) Illustration of initial terms: a(n) is also the area of the n-th region of an infinite diagram of compositions (ordered partitions) of the positive integers, where the length of the n-th horizontal line segment is equal to A001511(n) and the length of the n-th vertical line segment is equal to A006519(n), as shown below (first eight regions): ----------------------------- n a(n) Diagram ----------------------------- . _ _ _ _ 1 1 |_| | | | 2 3 |_ _| | | 3 1 |_| | | 4 7 |_ _ _| | 5 1 |_| | | 6 3 |_ _| | 7 1 |_| | 8 15 |_ _ _ _| . The above diagram represents the eight compositions of 4: [1,1,1,1],[2,1,1],[1,2,1],[3,1],[1,1,2],[2,2],[1,3],[4]. (End) MAPLE nmax:=98: for p from 0 to ceil(simplify(log[2](nmax))) do for n from 1 to ceil(nmax/(p+2)) do a((2*n-1)*2^p) := 2^(p+1)-1 od: od: seq(a(n), n=1..nmax); # Johannes W. Meijer, Feb 01 2013 MATHEMATICA Table[Denominator[DivisorSigma[1, 2*n]/DivisorSigma[1, n]], {n, 1, 128}] Table[BitXor[(n + 1), n], {n, 0, 100}] (* Vladimir Joseph Stephan Orlovsky, Jul 19 2011 *) PROG (C) int a(int n) { return n ^ (n-1); } // Russ Cox, May 15 2007 (Haskell) import Data.Bits (xor) a038712 n = n `xor` (n - 1) :: Integer -- Reinhard Zumkeller, Apr 23 2012 (PARI) vector(66, n, bitxor(n-1, n)) \\ Joerg Arndt, Sep 01 2013; corrected by Michel Marcus, Aug 02 2018 (Python) def A038712(n): return n^(n-1) # Chai Wah Wu, Jul 05 2022 CROSSREFS A038713 translated from binary, diagonals of A003987 on either side of main diagonal. Cf. A062383. Partial sums give A080277. Bisection of A089312. Cf. A088837. a(n)-1 is exponent of 2 in A089893(n). Cf. A130093. This is Guy Steele's sequence GS(6, 2) (see A135416). Cf. A001620, A168312, A220466. Sequence in context: A021991 A112132 A053381 * A354587 A065745 A268670 Adjacent sequences: A038709 A038710 A038711 * A038713 A038714 A038715 KEYWORD easy,nonn,mult,changed AUTHOR Henry Bottomley, May 02 2000 EXTENSIONS Definition corrected by N. J. A. Sloane, Sep 07 2015 at the suggestion of Marc LeBrun Name corrected by Wolfdieter Lang, Aug 30 2016 STATUS approved

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Last modified December 7 03:44 EST 2022. Contains 358649 sequences. (Running on oeis4.)