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 A078608 a(n) = ceiling( 2/(2^(1/n)-1)). 5
 2, 5, 8, 11, 14, 17, 20, 23, 25, 28, 31, 34, 37, 40, 43, 46, 49, 51, 54, 57, 60, 63, 66, 69, 72, 75, 77, 80, 83, 86, 89, 92, 95, 98, 100, 103, 106, 109, 112, 115, 118, 121, 124, 126, 129, 132, 135, 138, 141, 144, 147, 150, 152, 155, 158, 161, 164, 167, 170, 173, 176, 178, 181 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For n >= 2, a(n) = least positive integer x such that 2*x^n>(x+2)^n. For example, a(2)=5 as 4^2=16, 5^2=25, 6^2=36 and 7^2=49. Coincides with floor( 2*n/(log 2) ) for all n from 1 to 777451915729367 but differs at 777451915729368. See A129935. The first few values of n for which this sequence differs from floor( 2*n/(log 2) ) were found by Dean Hickerson in 2002. - N. J. A. Sloane, Apr 30 2014 The sequence floor( log(n)/(2*log(2)) ) is mentioned by Erdös and Selfridge (1973).  This sequence begins 0,0,0,1,1,1,1,... = 0 (3 times), 1 (12 times), 2 (48 times), 3 (192 times), 4 (768 times), ..., and grows too slowly to have its own entry. It is related to the game studied by Hales and Jewett (1963). - N. J. A. Sloane, Dec 02 2016. REFERENCES Erdös, Paul, and John L. Selfridge. "On a combinatorial game." Journal of Combinatorial Theory, Series A 14.3 (1973): 298-301. S. Golomb, "Martin Gardner and Tictacktoe," in Demaine, Demaine, and Rodgers, eds., A Lifetime of Puzzles, A K Peters, 2008, pp. 293-301. S. W. Golomb and A. W. Hales, "Hypercube Tic-Tac-Toe", in "More Games of No Chance", ed. R. J. Nowakowski, MSRI Publications 42, Cambridge University Press, 2002, pp. 167-182. Here it is stated that the first counterexample is at n=6847196937, an error due to faulty multiprecision arithmetic. The correct value was found by Dean Hickerson in 2002, and J. Buhler in 2004, and is reported in S. Golomb (2008). Hales, A. W., and Jewett, R. I., “Regularity and Positional Games,” Transactions of the American Mathematical Society, vol. 106, no. 2, Feb. 1963, 222-229. Dean Hickerson, Email to Jon Perry and N. J. A. Sloane, Dec 16 2002. Gives first three terms of A129935: 777451915729368, 140894092055857794, 1526223088619171207, as well as five later terms. - N. J. A. Sloane, Apr 30 2014 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 Max Alekseyev and others, Integer Parts [in Russian] Max Alekseyev and others, Integer Parts [in Russian] [Cached copy in pdf format] Art of Problem Solving, Logarithmic Identity S. W. Golomb and A. W. Hales, Hypercube Tic-Tac-Toe K. O'Bryant, The sequence of fractional parts of roots, arXiv preprint arXiv:1410.2927, 2014 MATHEMATICA Table[(Ceiling[2/(2^(1/n)-1)]), {n, 1, 100}] (* Vincenzo Librandi, May 01 2014 *) PROG (PARI) for (n=2, 50, x=2; while (2*x^n<=((x+2)^n), x++); print1(x", ")) (Haskell) a078608 = ceiling . (2 /) . (subtract 1) . (2 **) . recip . fromIntegral -- Reinhard Zumkeller, Mar 27 2015 CROSSREFS Cf. A078607, A078609, A129935. Sequence in context: A190336 A276889 A276877 * A189934 A189386 A292661 Adjacent sequences:  A078605 A078606 A078607 * A078609 A078610 A078611 KEYWORD nonn AUTHOR Jon Perry, Dec 09 2002 EXTENSIONS Edited by Dean Hickerson, Dec 17 2002 Revised by N. J. A. Sloane, Jun 07 2007 STATUS approved

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Last modified October 19 15:49 EDT 2018. Contains 316365 sequences. (Running on oeis4.)