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Search: id:A097647
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| A097647 |
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Non-palindromic numbers n such that phi(n)=phi(reversal(n)). |
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+0
2
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| 190, 427, 429, 724, 924, 4147, 4697, 6276, 6726, 7414, 7964, 9079, 9709, 10040, 10940, 14450, 15860, 19190, 20493, 20553, 28092, 28215, 29082, 35502, 39402, 41847, 42777, 44629, 46899, 49929, 51282, 51845, 53075, 54815, 57035, 57677
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If n is in the sequence and 10 doesn't divide n then reversal(n) is also in the sequence. There exists three terms of this sequence less than 180000000 that reversal of them are primes,i.e. 10040,14450 and 1865170. This sequence has 445 composite terms less than 20000000 and there is no prime term up to 222000000. Has this sequence at least one prime term?
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EXAMPLE
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10040 is in the sequence because phi(10040)=phi(4001)=4000.
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MATHEMATICA
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Do[If[n!=FromDigits[Reverse[IntegerDigits[n]]]&&EulerPhi[n]==EulerPhi[ FromDigits[Reverse[IntegerDigits[n]]]], Print[n]], {n, 80000}]
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CROSSREFS
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Cf. A097648, A085329.
Sequence in context: A025391 A025382 A051979 this_sequence A133241 A103494 A104642
Adjacent sequences: A097644 A097645 A097646 this_sequence A097648 A097649 A097650
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KEYWORD
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base,nonn
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AUTHOR
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Farideh Firoozbakht (f.firoozbakht(AT)math.ui.ac.ir), Aug 28 2004
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