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Search: id:A161594
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| 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 11, 21, 13, 41, 51, 61, 17, 81, 19, 2, 12, 22, 23, 42, 52, 26, 72, 82, 29, 3, 31, 23, 33, 241, 53, 63, 37, 281, 39, 4, 41, 24, 43, 44, 54, 46, 47, 84, 94, 5, 312, 421, 53, 45, 55, 65, 372, 481, 59, 6, 61, 62, 36, 46, 551, 66, 67, 482, 69, 7, 71, 27
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Might be called TITO(n), turning n inside out then turning outside in.
Here is the operation: take a number n and find its prime factors. Reverse the digits of every prime factor (for example, replace 17 by 71). Multiply the factors respecting multiplicities. For example, if the original number was 17^2*43^3, the new product will be 71^2*34^3. After that, reverse the resulting number.
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LINKS
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M. F. Hasler, Table of n, a(n) for n=1,...,5000. [From M. F. Hasler (MHasler(AT)univ-ag.fr), Jun 24 2009]
T. Khovanova, Turning Numbers Inside Out [From Tanya Khovanova (tanyakh(AT)yahoo.com), Jul 07 2009]
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FORMULA
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a(p) = p, for prime p.
Comment from M. F. Hasler, Jun 25 2009: a( p*10^k ) = p for any prime p.
Proof: * if gcd( p, 2*5) = 1, then a( p * 10^k ) = R( R(p) * R(2)^k * R(5)^k ) = R( R(p) * 10^k ) = R( R(p)) = p
* if gcd( p, 2*5) = 2, then p=2 and a( p * 10^k ) = R( R(2)^(k+1) * R(5)^k ) = R( 2 * 10^k ) = 2 = p and mutatis mutandis for gcd( p, 2*5) = 5.
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EXAMPLE
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a(34) = 241, because 34 = 2*17, f(34) = 2*71 = 142, and reversing gives 241.
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MAPLE
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read("transforms") ; A071786 := proc(n) local ifs, a, d ; ifs := ifactors(n)[2] ; a := 1 ; for d in ifs do a := a*digrev(op(1, d))^op(2, d) ; od: a ; end: A161594 := proc(n) digrev(A071786(n)) ; end: seq(A161594(n), n=1..80) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 16 2009]
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MATHEMATICA
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reversepower[{n_, k_}] := FromDigits[Reverse[IntegerDigits[n]]]^k f[n_] := FromDigits[ Reverse[IntegerDigits[Times @@ Map[reversepower, FactorInteger[n]]]]] Table[f[n], {n, 100}]
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PROGRAM
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Contribution from M. F. Hasler (MHasler(AT)univ-ag.fr), Jun 24 2009: (Start)
(PARI) A161594(n)={n=factor(n); n[, 1]=apply(R, n[, 1]); R(factorback(n))}
R(n)=eval(concat(vecextract(Vec(Str(n)), "-1..1"))) /* = A004086(n) */ (End)
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CROSSREFS
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Cf. A161597, A161598, A161600, A071786, A004086, A151764.
Sequence in context: A004151 A151765 A107603 this_sequence A084011 A004086 A121760
Adjacent sequences: A161591 A161592 A161593 this_sequence A161595 A161596 A161597
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KEYWORD
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nonn,base,nice
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AUTHOR
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J. H. Conway & Tanya Khovanova (tanyakh(AT)yahoo.com), Jun 14 2009
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EXTENSIONS
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Simpler definition from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 16 2009
Edited by N. J. A. Sloane, Jun 23 2009
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