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A053286
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Cototient of 2^n + 1.
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1
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1, 1, 1, 3, 1, 13, 17, 45, 1, 189, 225, 685, 257, 2733, 3841, 12969, 1, 43693, 75521, 174765, 61697, 731817, 848897, 2796205, 262145, 13304433, 14802689, 49449609, 15790337, 185023425, 313421825, 715827885, 6701057, 2957312961, 3551128577
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OFFSET
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0,4
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LINKS
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FORMULA
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MATHEMATICA
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Table[2^n + 1 - EulerPhi[2^n + 1], {n, 0, 50}] (* G. C. Greubel, May 31 2018 *)
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PROG
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(PARI) a(n) = my(x=2^n+1); x - eulerphi(x); \\ Michel Marcus, Aug 17 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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Offset changed to 0 and a(0) prepended by Amiram Eldar, Jan 11 2024
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STATUS
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approved
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