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 A231897 a(n) = smallest m such that wt(m^2) = n (where wt(i) = A000120(i)), or -1 if no such m exists. 4
 0, 1, 3, 5, 13, 11, 21, 39, 45, 75, 155, 217, 331, 181, 627, 923, 1241, 2505, 3915, 5221, 6475, 11309, 15595, 19637, 31595, 44491, 69451, 113447, 185269, 244661, 357081, 453677, 1015143, 908091, 980853, 2960011, 4568757, 2965685, 5931189, 11862197, 20437147 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Conjecture: a(n) is never -1. (It seems likely that the arguments of LindstrÃ¶m (1997) could be modified to establish this conjecture.) a(n) is the smallest m such that A159918(m) = n (or -1 if ...). LINKS Donovan Johnson, Table of n, a(n) for n = 0..70 Bernt LindstrÃ¶m, On the binary digits of a power, Journal of Number Theory, Volume 65, Issue 2, August 1997, Pages 321-324. PROG (Haskell) a231897 n = head [x | x <- [1..], a159918 x == n] -- Reinhard Zumkeller, Nov 20 2013 (PARI) a(n)=if(n, my(k); while(hammingweight(k++^2)!=n, ); k, 0) \\ Charles R Greathouse IV, Aug 06 2015 CROSSREFS Cf. A000120, A159918, A230097, A231898, A214560. Sequence in context: A263829 A028268 A171424 * A260416 A256222 A258976 Adjacent sequences:  A231894 A231895 A231896 * A231898 A231899 A231900 KEYWORD nonn AUTHOR N. J. A. Sloane, Nov 19 2013 EXTENSIONS a(26-40) from Reinhard Zumkeller, Nov 20 2013 STATUS approved

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Last modified June 17 22:17 EDT 2019. Contains 324200 sequences. (Running on oeis4.)