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A289275
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Numbers k such that the deficiency of k^2 is itself a square.
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4
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1, 2, 4, 8, 16, 32, 46, 64, 128, 256, 284, 512, 1024, 1633, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 149728, 242656, 260495, 262144, 298057, 524288, 1048576, 1056752, 2097152, 4194304, 8388608, 9587584, 16777216, 17706256, 33554432, 67108864, 134217728
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OFFSET
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1,2
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COMMENTS
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The sequence of square roots of the deficiencies of this sequence is A288145.
The current sequence is the disjoint union of the powers of 2 (A000079) and the sequence A289274.
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LINKS
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MATHEMATICA
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Select[Range[10^5], IntegerQ@ Sqrt[2 #^2 - DivisorSigma[1, #^2]] &] (* Michael De Vlieger, Jul 04 2017 *)
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PROG
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(PARI) isok(n) = issquare(2*n^2 - sigma(n^2)); \\ Michel Marcus, Jul 01 2017
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CROSSREFS
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Square roots of deficiencies of squares is A288145.
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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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