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A045504
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Palindromic Fibonacci numbers.
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4
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OFFSET
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1,4
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COMMENTS
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Also, Luca proved that 0,1,1,2,3,5,8,55 are the only Fibonacci numbers containing a single distinct digit.
Probably 55 is the last term. Indices of the palindromic Fibonacci numbers are 0,1,2,3,4,5,6,10. - Robert G. Wilson v, Jun 29 2007.
There are no further terms up to Fibonacci(10^8), found in 36 processor minutes. Note that one typically only needs to check a few digits at the start and the end to rule out being a palindrome. [D. S. McNeil, Dec 30 2010]
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LINKS
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EXAMPLE
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55 is the 10th Fibonacci number and it is also palindromic in base 10.
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MATHEMATICA
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fQ[n_] := Block[{id = IntegerDigits@ Fibonacci@ n}, id == Reverse@ id]; lst = {}; Do[ If[ fQ@n, AppendTo[lst, n]], {n, 0, 1000}]; Fibonacci /@ lst (* Robert G. Wilson v *)
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PROG
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(Magma) IsPalindromic := func<Fn|forall{i:i in[1..d div 2]|digit_seq[i]eq digit_seq[d+1-i]}where d is #digit_seq where digit_seq is IntegerToString(Fn)>; [Fn:n in[1..10^4]|IsPalindromic(Fn)where Fn is Fibonacci(n)]; /* Jason Kimberley */
(PARI) ispal(n)=my(d=digits(n)); for(i=1, #d\2, if(d[i]!=d[#d+1-i], return(0))); 1
is(n)=my(k=n^2); k+=(k+1)<<2; n >= 0 && (issquare(k) || issquare(k-8)) && ispal(n) \\ Charles R Greathouse IV, Feb 04 2013
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CROSSREFS
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KEYWORD
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nonn,base,more,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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