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Search: id:A087473
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| A087473 |
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Smallest number that requires n iterations of f(k) to reach a single digit, where f(k) is the product of the two numbers formed from the alternating digits of k. |
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+0
4
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| 1, 10, 25, 39, 77, 171, 199, 577, 887, 1592, 2682, 3988, 6913, 18747, 39577, 58439, 99428, 173442, 267343, 299137, 574182, 685812, 880543, 1635812, 1974447, 2771717, 18871813, 45797337, 49899368, 58935768
(list; graph; listen)
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OFFSET
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0,2
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EXAMPLE
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a(4)= 77 since 77 is the smallest number that requires 4 iterations to reach a single digit: f(77)=7*7=49, f(49)=4*9=36, f(36)=3*6=18, f(18)=1*8=8.
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CROSSREFS
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Cf. A087471, A087472, A087474.
Sequence in context: A014090 A074814 A002600 this_sequence A014120 A003001 A038350
Adjacent sequences: A087470 A087471 A087472 this_sequence A087474 A087475 A087476
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com) and Paul D. Hanna (pauldhanna(AT)juno.com), Sep 11 2003
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EXTENSIONS
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More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 19 2003
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