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A231897
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a(n) = smallest m such that wt(m^2) = n (where wt(i) = A000120(i)), or -1 if no such m exists.
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8
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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
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OFFSET
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0,3
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COMMENTS
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Conjecture: a(n) is never -1. (It seems likely that the arguments of Lindström (1997) could be modified to establish this conjecture.)
a(n) is the smallest m such that A159918(m) = n (or -1 if ...).
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LINKS
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Hugo Pfoertner, Table of n, a(n) for n = 0..110 (terms 0..70 from Donovan Johnson, significant extension enabled by programs provided in Code Golf challenge).
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FORMULA
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PROG
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(Haskell)
a231897 n = head [x | x <- [1..], a159918 x == n]
(Python)
def wt(n): return bin(n).count('1')
def a(n):
m = 2**(n//2) - 1
while wt(m**2) != n: m += 1
return m
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CROSSREFS
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A089998 are the corresponding squares.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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