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A101641
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Positive integers n for which n = f(n), where f(n) is the total number of 4's required when writing out all numbers between 0 and n.
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14
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499999984, 499999985, 499999986, 499999987, 499999988, 499999989, 499999990, 499999991, 499999992, 499999993, 500000000, 10000000000, 10499999984, 10499999985, 10499999986, 10499999987, 10499999988, 10499999989
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OFFSET
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1,1
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COMMENTS
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Related to a problem posed by Google and discussed on the MathWorld link.
Together with the b-file, this gives the complete list of all 47 positive numbers n such that n is equal to the number of 4's in the decimal digits of all numbers <= n. - Daniel Hirschberg (dan(AT)ics.uci.edu), May 05 2007
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LINKS
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FORMULA
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a(n) = 499999983 + n, n <= 10; a(n) = 500000000, n = 11
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EXAMPLE
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a(1) = 499999984, since writing out all numbers from 0 to 499999984 requires that 499999984 4's be used and since 499999984 is the first such positive integer.
a(4) = 499999987 because the number of 4's in the decimal digits of the numbers from 1 to 499999987 is 499999987 and this is the 4th such number.
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CROSSREFS
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KEYWORD
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nonn,base,fini,full
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AUTHOR
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EXTENSIONS
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More terms from Daniel Hirschberg (dan(AT)ics.uci.edu), May 05 2007
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STATUS
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approved
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