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A004770
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Numbers of the form 8k+5; or, numbers whose binary expansion ends in 101.
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29
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5, 13, 21, 29, 37, 45, 53, 61, 69, 77, 85, 93, 101, 109, 117, 125, 133, 141, 149, 157, 165, 173, 181, 189, 197, 205, 213, 221, 229, 237, 245, 253, 261, 269, 277, 285, 293, 301, 309, 317, 325, 333, 341, 349, 357, 365, 373, 381, 389, 397, 405, 413, 421, 429
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OFFSET
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1,1
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COMMENTS
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Only numbers of the form 8k+5 may be written as a sum of 5 odd squares. Examples: 5 = 1+1+1+1+1, 13 = 9+1+1+1+1, 21 = 9+9+1+1+1, 29 = 25+1+1+1+1= 9+9+9+1+1, 37 = 9+9+9+9+1 = 25+9+1+1+1, 45 = 25+9+9+1+1=9+9+9+9+9, 53 = 49+1+1+1+1 = 25+25+1+1+1 = 25+9+9+9+1, ... - Philippe Deléham, Sep 03 2005
Positive solutions to the equation x == 5 (mod 8). - K.V.Iyer, Apr 27 2009
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LINKS
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FORMULA
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a(n) = 8*n - 3.
G.f.: x*(5+3*x)/(x-1)^2. (End)
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MATHEMATICA
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LinearRecurrence[{2, -1}, {5, 13}, 60] (* or *) NestList[#+8&, 5, 60] (* Harvey P. Dale, Jun 28 2021 *)
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PROG
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(Haskell)
a004770 = (subtract 3) . (* 8)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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