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A101639
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Positive integers n for which n = f(n), where f(n) is the total number of 2's required when writing out all numbers between 0 and n.
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10
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28263827, 35000000, 242463827, 500000000, 528263827, 535000000, 10000000000, 10028263827, 10035000000, 10242463827, 10500000000, 10528263827, 10535000000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Related to a problem posed by Google and discussed on the MathWorld link.
This is the complete list of all 13 positive numbers n such that n is equal to the number of 2's in the decimal digits of all numbers <= n. - Daniel Hirschberg (dan(AT)ics.uci.edu), May 05 2007
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LINKS
| Mathworld, A problem posed by Google
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EXAMPLE
| a(1) = 28263827 since writing out all numbers from 0 to 28263827 requires that 28263827 2's be used and since 28263827 is the first such positive integer.
a(4)=500000000 because the number of 2's in the decimal digits of the numbers from 1 to 500000000 is 500000000 and this is the 4th such number.
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CROSSREFS
| Cf. A014778 for proof these sequences are finite; Also A101640, A101641, A130427, A130428, A130429, A130430, A130431; cf. A130432 for the number of numbers in these sequences.
Sequence in context: A204805 A114681 A205933 * A112640 A200217 A104828
Adjacent sequences: A101636 A101637 A101638 * A101640 A101641 A101642
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KEYWORD
| base,fini,nonn,full
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AUTHOR
| Ryan Propper (rpropper(AT)stanford.edu), Dec 10 2004
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EXTENSIONS
| More terms from Daniel Hirschberg (dan(AT)ics.uci.edu), May 05 2007
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