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A280647
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Numbers k such that k^3 has an odd number of digits and the middle digit is 7.
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3
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31, 32, 105, 111, 128, 130, 149, 167, 173, 191, 192, 475, 483, 484, 491, 509, 524, 530, 534, 545, 546, 550, 556, 559, 584, 590, 592, 597, 614, 619, 624, 628, 637, 641, 665, 668, 692, 701, 725, 743, 750, 760, 781, 793, 809, 824, 836, 837, 843, 852, 861, 864
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OFFSET
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1,1
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COMMENTS
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The sequence of cubes starts: 29791, 32768, 1157625, 1367631, 2097152, 2197000, 3307949, 4657463, ...
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LINKS
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EXAMPLE
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31^3 = 29(7)91, 191^3 = 696(7)871, 619^3 = 2371(7)6659.
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MATHEMATICA
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Select[Range[865], OddQ[len=Length[IntegerDigits[#^3]]]&&Part[IntegerDigits[#^3], (len+1)/2]==7 &] (* Stefano Spezia, Oct 03 2023 *)
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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