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A097648
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a(n) is the least non-palindromic number m such that phi(m)=phi(reversal(m))=4*10^(n+2), or 0 if no such number exists.
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1
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10040, 110440, 1014040, 11154440, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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OFFSET
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1,1
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COMMENTS
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It seems that 10 divides all terms of this sequence.
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LINKS
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Table of n, a(n) for n=1..49.
C. Rivera, f(p)=f(p') , puzzle 282
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FORMULA
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a[n_]:=(For[m=4*10^(n+2), !(m!=FromDigits[Reverse[IntegerDigits[m]]] &&EulerPhi[m]==EulerPhi[FromDigits[Reverse[IntegerDigits [m]]]]==4*10^(n+2)), m++ ];m)
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EXAMPLE
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a(4)=11154440 because phi(11154440)=phi(04445111)=4000000 and 11154440 is the earliest non-palindromic number with this property.
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MATHEMATICA
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a[n_]:=(For[m=4*10^(n+2), !(m!=FromDigits[Reverse[IntegerDigits[m]]] &&EulerPhi[m]==EulerPhi[FromDigits[Reverse[IntegerDigits [m]]]]==4*10^(n+2)), m++ ]; m); Do[Print[a[n]], {n, 4}]
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CROSSREFS
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Subsequence of A097647.
Sequence in context: A251136 A213318 A346026 * A188663 A250711 A223431
Adjacent sequences: A097645 A097646 A097647 * A097649 A097650 A097651
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KEYWORD
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base,nonn,more
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AUTHOR
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Farideh Firoozbakht, Sep 04 2004
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EXTENSIONS
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Better definition and more terms from David Wasserman, Dec 28 2007
a(27)-a(49) from Max Alekseyev, Oct 17 2008; Aug 15 2013; Jun 14 2022
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STATUS
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approved
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