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 A097648 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. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS It seems that 10 divides all terms of this sequence. LINKS C. Rivera, f(p)=f(p') , puzzle 282 FORMULA 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) EXAMPLE a(4)=11154440 because phi(11154440)=phi(04445111)=4000000 and 11154440 is the earliest non-palindromic number with this property. MATHEMATICA 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}] CROSSREFS Subsequence of A097647. Sequence in context: A251136 A213318 A346026 * A188663 A250711 A223431 Adjacent sequences: A097645 A097646 A097647 * A097649 A097650 A097651 KEYWORD base,nonn,more AUTHOR Farideh Firoozbakht, Sep 04 2004 EXTENSIONS 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 STATUS approved

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Last modified March 23 23:09 EDT 2023. Contains 361454 sequences. (Running on oeis4.)