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A087471
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Final digit resulting from iterations of the product of the two numbers formed from the alternating digits of n.
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4
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1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 2, 4, 6, 8, 0, 2, 4, 6, 8, 0, 3, 6, 9, 2, 5, 8, 2, 8, 4, 0, 4, 8, 2, 6, 0, 8, 6, 6, 8, 0, 5, 0, 5, 0, 0, 0, 5, 0, 0, 0, 6, 2, 8, 8, 0, 8, 8, 6, 0, 0, 7, 4, 2, 6, 5, 8, 8, 0, 8, 0, 8, 6, 8, 6, 0, 6, 0, 8, 4, 0, 9, 8, 4, 8, 0, 0, 8, 4, 8, 0, 0, 0, 0, 0, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A087472(n) gives the number of iterations required for Murthy's function, f(n), to reach a single digit. A087473(n) gives the smallest number that requires n iterations of Murthy's function to reach a single digit. The n-th row of triangle A087474 gives the n successive iterations of Murthy's function on A087473(n).
Apart from the undefined a(0), the sequence differs from A031347 first at n=121. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 11 2008]
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FORMULA
| a(n) = a(f(n)), where f(n) is Murthy's function: f(1234)=13*24=312, f(12345)=135*24=3240, f(123456)=135*246=33210.
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EXAMPLE
| a(1234) = a(13*24) = a(312) = a(32*1) = a(32) = a(3*2) = 6.
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CROSSREFS
| Cf. A087472, A087473, A087474.
Sequence in context: A175420 A062078 A031347 * A128212 A187844 A007954
Adjacent sequences: A087468 A087469 A087470 * A087472 A087473 A087474
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KEYWORD
| nonn,base
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com) and Paul D. Hanna (pauldhanna(AT)juno.com), Sep 11 2003
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