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A064870
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The minimal number which has multiplicative persistence 6 in base n.
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6
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11262, 57596799, 30536, 6788, 4684, 1571, 439, 667, 1964, 683, 218, 857, 264, 278, 353, 393, 227, 382, 344, 311, 319, 307, 283, 417, 422, 381, 485, 436, 349, 431, 436, 449, 421, 469, 327, 575, 598, 483, 539, 413, 511, 517, 534, 641, 611, 609, 476, 479
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OFFSET
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7,1
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COMMENTS
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The persistence of a number is the number of times you need to multiply the digits together before reaching a single digit. a(5)=1811981201171874, a(6) seems not to exist.
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LINKS
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Table of n, a(n) for n=7..54.
M. R. Diamond and D. D. Reidpath, A counterexample to a conjuncture of Sloane and Erdos, J. Recreational Math., 1998 29(2), 89-92. [Broken link?]
Sascha Kurz, Persistence in different bases
C. Rivera, Minimal prime with persistence p
N. J. A. Sloane, The persistence of a number, J. Recreational Math., 6 (1973), 97-98.
Eric Weisstein's World of Mathematics, Multiplicative Persistence
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FORMULA
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a(n) = 7*n-[n/720] for n > 719
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EXAMPLE
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a(13)=439 because 439=[2'7'10]->[10'10]->[7'9]->[4'11]->[3'5]->[1'2]->[2] needs 6 steps and no fewer n.
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CROSSREFS
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Cf. A003001, A031346, A064867, A064868, A064869, A064871, A064872.
Sequence in context: A185797 A135015 A104316 * A051520 A051346 A217125
Adjacent sequences: A064867 A064868 A064869 * A064871 A064872 A064873
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KEYWORD
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base,easy,nonn
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AUTHOR
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Sascha Kurz, Oct 08 2001
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STATUS
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approved
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