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%I #16 Sep 01 2021 22:20:54
%S 1409794,68889,38200,17902874277,1494,2532,19526,15838,1101,15820,943,
%T 2674,2118,3275,412,3310,1593,440,478,2036,456,713,738,633,658,705,
%U 907,643,803,641,653,797,484,991,814,877,1079,767,840,575,930,843,710,880
%N The minimal number which has multiplicative persistence 7 in base n.
%C The persistence of a number is the number of times you need to multiply the digits together before reaching a single digit. a(7) = 686285, a(8) seems not to exist.
%H M. R. Diamond and D. D. Reidpath, <a href="http://www.mathe2.uni-bayreuth.de/sascha/oeis/persistence/PERSIST.PDF">A counterexample to a conjecture of Sloane and Erdos</a>, J. Recreational Math., 1998 29(2), 89-92.
%H Sascha Kurz, <a href="http://www.mathe2.uni-bayreuth.de/sascha/oeis/persistence/persistence.html">Persistence in different bases</a>
%H T. Lamont-Smith, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL24/Lamont/lamont5.html">Multiplicative Persistence and Absolute Multiplicative Persistence</a>, J. Int. Seq., Vol. 24 (2021), Article 21.6.7.
%H C. Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_022.htm">Minimal prime with persistence p</a>
%H N. J. A. Sloane, <a href="http://neilsloane.com/doc/persistence.html">The persistence of a number</a>, J. Recreational Math., 6 (1973), 97-98.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/MultiplicativePersistence.html">Multiplicative Persistence</a>
%F a(n) = 8*n-[n/5040] for n > 5039.
%e a(9) = 1409794 because the persistence of 1409794 is 7.
%Y Cf. A003001, A031346, A064867, A064868, A064869, A064870, A064872.
%K base,easy,nonn
%O 9,1
%A _Sascha Kurz_, Oct 08 2001
%E Corrected by _R. J. Mathar_, Nov 02 2007