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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. +0
2
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 (list; graph; listen)
OFFSET

1,1

COMMENT

This sequence is a subsequence of A097647. It seems that 10 divides all terms of this sequence. Conjecture: This sequence is infinite.

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

Cf. A097647.

Sequence in context: A052095 A033533 A146505 this_sequence A023356 A145836 A157288

Adjacent sequences: A097645 A097646 A097647 this_sequence A097649 A097650 A097651

KEYWORD

more,nonn

AUTHOR

Farideh Firoozbakht (mymontain(AT)yahoo.com), Sep 04 2004

EXTENSIONS

Better definition and more terms from David Wasserman (dwasserm(AT)earthlink.net), Dec 28 2007

a(27)=a(28)=...=a(32)=0 from Max Alekseyev (maxale(AT)gmail.com), Oct 17 2008

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Last modified December 20 00:58 EST 2009. Contains 171054 sequences.


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