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Search: id:A054756
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| A054756 |
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Totient(n) and cototient(n) are squares but n is not in A054755. |
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1
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| 1, 468, 1417, 1872, 2340, 3145, 4100, 4212, 7488, 9360, 14841, 15588, 16400, 16848, 20329, 21060, 29952, 31417, 37440, 37908, 45097, 49833, 58500, 62352, 63529, 63945, 65600, 67392, 69700, 78625, 79092, 83569, 84169, 84240, 88929, 102500
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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Phi[a(n)]=x^2, a(n)-Phi[a(n)]=y^2, a(n) is not an odd power of prime from A002496.
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EXAMPLE
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An even number is 2340=4*9*5*13 [totient and cototient is 576 or 1764 (24^2, 42^2)]. An odd number is 14841=9*17*97 [Phi=9216=96^2, cototient=5625=75*75].
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MATHEMATICA
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Select[ Range[ 1, 200000 ], IntegerQ[ Sqrt[ eu[ # ] ] ]&& IntegerQ[ Sqrt[ co[ # ] ] ]&&!Equal[ lfi[ # ], 1 ]& ], where eu[ x_ ] =EulerPhi[ x ], co[ x_ ]=x-EulerPhi[ x ] and lfi[ x_ ]=Length[ FactorInteger[ x ] ]
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CROSSREFS
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Cf. A000010, A051953, A039770, A002496, A005574.
Equals A054754 \setminus A054755. See also A063752.
Sequence in context: A059395 A114135 A043364 this_sequence A045305 A112297 A104744
Adjacent sequences: A054753 A054754 A054755 this_sequence A054757 A054758 A054759
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Apr 25 2000
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