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Search: id:A133422
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| A133422 |
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Number of steps to reach 1 under repeated applications of the "7x+1" map of A133421, or -1 if 1 is never reached. |
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+0
2
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| 0, 1, 1, 2, 1, 2, 4, 3, 2, 2, 12, 3, 9, 5, 2, 4, 6, 3, 21, 3, 5, 13, 6, 4, 2, 10, 3, 6, 10, 3, 47, 5, 13, 7, 5, 4, 13, 22, 10, 4, 8, 6, 46, 14, 3, 7, 16, 5, 50, 3
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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The 7x+1 map sends x to x/2 if x is even, x/3 if x is divisible by 3, x/5 if x is divisible by 5, otherwise 7x+1.
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LINKS
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Tomas Oliveira e Silva, The px+1 problem
Index entries for sequences related to 3x+1 (or Collatz) problem
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MATHEMATICA
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nxt[x_]:= Which[Mod[x, 2]==0, x/2, Mod[x, 3]==0, x/3, Mod[x, 5]==0, x/5, True, 7x+1]; Table[First[First[Position[NestList[nxt, i, 100], 1]]]-1, {i, 50}] - Harvey P. Dale (hpd1(AT)nyu.edu), Dec 27 2007
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CROSSREFS
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Cf. A133421, A133419, ...
Adjacent sequences: A133419 A133420 A133421 this_sequence A133423 A133424 A133425
Sequence in context: A091173 A101897 A078142 this_sequence A099312 A117505 A131380
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KEYWORD
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nonn,easy,more
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AUTHOR
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njas, Nov 27 2007
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EXTENSIONS
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More terms from Harvey P. Dale (hpd1(AT)nyu.edu), Dec 27 2007
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