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Search: id:A130081
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| A130081 |
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Smallest number whose seventh power has at least n digits. |
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+0
2
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| 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; listen)
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OFFSET
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1,2
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COMMENT
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Powers of seventh root of 10 rounded up.
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FORMULA
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a(n) = ceiling(10^((n-1)/7))
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EXAMPLE
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1^7 = 1 has 1 digit, 2^7 = 128 has three digits, hence a(2) = a(3) = 2.
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PROGRAM
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(MAGMA) [ Ceiling(Root(10^(n-1), 7)): n in [1..44] ];
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CROSSREFS
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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: A116902 A066447 A035542 this_sequence A141847 A089333 A098492
Adjacent sequences: A130078 A130079 A130080 this_sequence A130082 A130083 A130084
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KEYWORD
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nonn,base,easy
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 07 2007
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