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 A130081 Smallest number whose seventh power has at least n digits. 2
 1, 2, 2, 3, 4, 6, 8, 10, 14, 20, 27, 38, 52, 72, 100, 139, 194, 269, 373, 518, 720, 1000, 1390, 1931, 2683, 3728, 5180, 7197, 10000, 13895, 19307, 26827, 37276, 51795, 71969, 100000, 138950, 193070, 268270, 372760, 517948, 719686, 1000000, 1389496 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Powers of seventh root of 10 rounded up. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 FORMULA a(n) = ceiling(10^((n-1)/7)). EXAMPLE 1^7 = 1 has 1 digit, 2^7 = 128 has three digits, hence a(2) = a(3) = 2. MATHEMATICA Table[(Ceiling[10^((n - 1)/7)]), {n, 1, 60}] (* Vincenzo Librandi, Sep 20 2013 *) PROG (Magma) [ Ceiling(Root(10^(n-1), 7)): n in [1..44] ]; CROSSREFS Cf. A011557 (powers of 10), A017936 (smallest number whose square has n digits), A018005 (smallest number whose cube has n digits), A018074 (smallest number whose fourth power has n digits), A018143 (smallest number whose fifth power has n digits), A130080 to A130084 (smallest number whose sixth ... tenth power has n digits). Sequence in context: A066447 A035542 A225484 * A141847 A182372 A089333 Adjacent sequences: A130078 A130079 A130080 * A130082 A130083 A130084 KEYWORD nonn,base,easy AUTHOR Klaus Brockhaus, May 07 2007 STATUS approved

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Last modified February 23 01:12 EST 2024. Contains 370265 sequences. (Running on oeis4.)