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 A064870 The minimal number which has multiplicative persistence 6 in base n. 6
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 7,1 COMMENTS 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. LINKS 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 FORMULA a(n) = 7*n-[n/720] for n > 719 EXAMPLE 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. CROSSREFS 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 KEYWORD base,easy,nonn AUTHOR Sascha Kurz, Oct 08 2001 STATUS approved

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