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Search: id:A117817
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| A117817 |
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Let T_n be the infinite sequence formed by starting with 1 and repeatedly reversing the digits and adding n to get the next term. If T_n eventually reaches a cycle, sequence gives length of that cycle, otherwise -1. |
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+0
72
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| 9, 81, 3, 54, 207, 30, 63, 27, 1, -1, 9, 15, 18, 72, -1, 90, 54, 13, 18, -1, 15, 9, 9, 36, 45, 18, 9, 36, 18, -1, 9, 9, 3, 36, 72, 2, 27, 18, 3, -1, 18, 57, 63, 9, 22, 90, 18, 30, 54, -1, 6, 99, 54, 13, 36, 207, 12, 63, 45, -1, 36, 27, 30, 108, 36, 264, 99, 36, 3, -1, 18, 22, 45, 90, 12, 45, 117, 192, 18, -1, 36, 45, 63, 168, 1008, 36, 24, 306, 9, -1, 99, 639, 36, 54, 144, 18, 225, 468, 1, -1, 18, 300, 189, 171, 765, 90, 45, 462, 90, -1, 9, 513, 63, 69
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(multiple of 10) = -1 (see A117816). a(15) = -1 (see A118532). a(n) is a multiple of 9/gcd(9,n) unless it is -1. - Martin Fuller (martin_n_fuller(AT)btinternet.com), May 12 2006
For a discussion of the -1 entries see A117816.
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LINKS
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N. J. A. Sloane, Sequences of RADD type
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MATHEMATICA
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ReverseNum[n_] := FromDigits[Reverse[IntegerDigits[n]]]; maxLen=10000; Table[z=1; lst={1}; While[z=ReverseNum[z]+n; !MemberQ[lst, z] && Length[lst]<maxLen, AppendTo[lst, z]]; If[Length[lst]<maxLen, Length[lst]-Position[lst, z][[1, 1]]+1, -1], {n, 100}] (Noe)
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CROSSREFS
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See A117817 for the -1 entries and cross-references to T_1 through T_16.
Sequence in context: A018913 A127265 A055070 this_sequence A107346 A014393 A008463
Adjacent sequences: A117814 A117815 A117816 this_sequence A117818 A117819 A117820
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KEYWORD
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sign,base
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AUTHOR
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njas, following discussions with Luc Stevens, May 04 2006
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EXTENSIONS
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a(21)-a(33) from Luc Stevens, May 08 2006
a(33) onwards from T. D. Noe (noe(AT)sspectra.com) and Martin Fuller (martin_n_fuller(AT)btinternet.com), May 10 2006
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